Yes you need to! And you need to be careful not to forgot that when doing your calculations!!
2/3 is basically 0.6666666667 which is the same as 66% so any percentage bigger than 66% such as 75% (0.75) which is 3/4 (as a fraction) is bigger than 2/3
1. x=5/2
2. x=3/4-3/4y
y belongs R
The answer would be, x = -14