## anonymous one year ago A and B are vertical angles. If A = 4x - 10 and B = 6x - 30, find mA.

1. Nnesha

pic ??

2. Nnesha

vertical angles are equal

3. anonymous

There is no picture.

4. Nnesha

alright so a and b are vertical angles vertical angles share the same vertex |dw:1434116295080:dw| for example here ^^^ a = b c=d a and are vertical angles and c and d are vertical equal so they are equal to each other $\huge\rm 4x-10=6x-30$ solve for x

5. anonymous

So when I solve 4x-10 i get 2.5 and when i solve 6x-30 i get 5.

6. Nnesha

wait what ? how did you get 2.5 and why did you solve it separately ?

7. anonymous

I divided 10 by 4 & i got 2.5

8. Nnesha

no no no! 4x MINUS 10 you can't divide by 10

9. Nnesha

write all x value to the one side of equal sign and constant term to the other side *constant term (number without variable )

10. Nnesha

$\huge\rm 4x-10=6x-30$ subtract 4x both sides

11. anonymous

There is a theorem that states two vertical angles are congruent, i.e. have the same angle measure. Thus A = B. Substituting in the values we have for A and B you get a linear equation that can be solved to find x. 4x - 10 = 6x - 30 -10 = 2x - 30 20 = 2x 10 = x Now that we know x, substitute back into the expression for A. A = 4x - 10 = 4*10 - 10 = 40 - 10 = 30 mA = 30

12. anonymous

Thank you.

13. Nnesha

remember to cancel out addition === >opposite subtraction multiplication ===> opposite division

14. Nnesha

so to cancel 4x from left side you should subtract 4x both sides :-)

15. Nnesha

|dw:1434117089054:dw| let me know what you get

16. anonymous

x=20

17. Nnesha

18. anonymous

|dw:1434117408586:dw|

19. anonymous

|dw:1434117516941:dw|

20. Nnesha

alright thanks! and combine like terms are add or subtract coefficient of SAME varaible 6x-30 <--- you can't subtract because 6 have x and 30 doesn't have x |dw:1434117600094:dw| there is NEGATIVE 30 at right side how would you move that to the left side ???

21. Nnesha

add or subtract 30 both sides ?

22. anonymous

23. Nnesha

yep add 30 both sides |dw:1434117716411:dw| still... we have to isolate x so how would you cancel out 2 from the right side ?? :-)

24. anonymous

|dw:1434117733194:dw|

25. Nnesha

yep yep divide! you got it!! so x = ??

26. anonymous

x=10

27. Nnesha

yep now be careful x=10 but they want us to find A so substitute x value in this equation $\large\rm A =4x-10$

28. anonymous

so the answer is A=10? lol i dont know

29. Nnesha

nope x=10 you need mA so replace x by 10 A=4x-10 and then solve for A

30. Nnesha

$\huge\rm A=4\color{green}{x}-10$ plug in 10

31. anonymous

|dw:1434118220477:dw|

32. Nnesha

:-)yaya!

33. anonymous

i get it!

34. Nnesha

yeah :-)gO_Od job!

35. anonymous

Lol thank you.