## lillywazhere 4 years ago -7/20f+2/5=1/4f what does f equal (show work) 4

1. myininaya

$-\frac{7}{20}f+\frac{2}{5}=\frac{1}{4}f$ get your f's together add 7f/20 on both sides $\frac{2}{5}=\frac{1}{4}f+\frac{7}{20}f$ find a common denominator $\frac{2}{5}=\frac{5}{20}f+\frac{7}{20}f$ $\frac{2}{5}=\frac{12}{20}f$ we can simplify 12/12 $\frac{2}{5}=\frac{3}{5}f$ $\frac{5}{3}*\frac{2}{5}=f$

2. A7med

2/5=1/4f+7/20f 2/5=5/20f+7/20f 2/5=12/20f 4f=60 f=15

3. myininaya

i get f=2/3 lets check

4. A7med

40f=60 f=3/2

5. myininaya

a7med did you do f=20/12*2/5

6. A7med

20f*2=5*12

7. myininaya

so you tried to cross multipliy so it should be 5*12f=2*20

8. lillywazhere

thank u

9. A7med

no, u 20f*2=5*12 i'm sure

10. myininaya

we have 12f/20=2/5 to get f by itself we multiplied by the reciprocal of 12/20 on both sides giving us (20/12)(12f/20)=(20/12)(2/5) f=40/60=2/3

11. myininaya

we can also check f=2/3 so we plug 2/3 whereever we see an f in the orignal problem (-7/20)(2/3)+2/5=(1/4)(2/3) -14/60+2/5=2/12 -7/30+2/5=2/12 -7/30+12/30=2/12 5/30=2/12 1/6=1/6 2/3 is definitely correct!