You just have to make equal fractions, so if c = 4 that means [tex]\frac{a}{5}[/tex] = [tex]\frac{4}{7}[/tex] so cross multiply to get 7a = 20; divide both sides by 7 to get a = 2.86 and do the same with the other ones
If c = 11 then [tex]\frac{a}{5}[/tex] = [tex]\frac{11}{7}[/tex] cross multiply to get 7a = 55; divide both sides by 7 to get a = 7.86 and so on
The answer is true to the other question
Hope this helps :)
