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Ok you might want to draw them as lines, that helps me anyway. I'll do 45 c and 46 b for you.
1. Find the longest chain.
2. Look for unsaturations in this chain.
3. Look for substituents on this chain.
The longest chain is 4, which means "but". There are no unsaturations, which means "ane". There is a methyl group. Start counting from the side closer to the methyl group. This makes it on the 2nd carbon. So the name is 2-methylbutane.
The longest chain is 5, which means "pent". There is an unsaturation: a double bond, which means "ene". So start counting from the side closer to the unsaturation (if there were a substituent, the unsaturation takes priority). This makes the double bond at the second carbon. There are no substituents. So the name is pent-2-ene.
I recommend the khan academy videos if you're having trouble with this.