To find two equivalent fractions you'll need to make their denominators(numbers below the line) same number.
So, think of a numbers you need to multiply 5 and 7 by, so that you get the same number. Common denominator for 5 and 7 is 35.
Multiply the first fraction by 7 and you get 2*7/5*7=14/35
Multiply the second fraction by 5 and you get 3*5/7*5=15/35
(do not forget that you have to multiply both numerator and denominator with the same number)
If you're not sure which number is the common denominator try this:
write numbers next to each other and then divide them until you get 1.
5 7]:5
1 7]:7
1 1
now multiply two numbers on the right(ones you divided with)
and you get 5*7=35
