Question 969428
The ratio of their ages now is 7x/8x, so we need to find x

14 years ago  ( 7x-14)/(8x-14)  the ratio was 7/9

This is a proportion problem solved with cross multiplication.

(7x-14) *9=(8x-14) *7

Distribute
63x-126=56x -98
solve by first moving the x over, subtracting 56x from both sides
7x-126=-98
add 126 to both sides
7x=28

x=4
The ratio is 7x/8x, so Mina is 28.  That is the answer asked for.

Her sister is now 32

14 years ago, Mina was 14 and her sister 18.  That is a 7:9 ratio.