a, y + 37m\(^2\) + 13m\(^2\) = 91dam\(^2\)
=> y + 37m\(^2\) + 13m\(^2\) = 9100m\(^2\)
=> y = 9100m\(^2\) - 37m\(^2\) - 13m\(^2\)
=> y = 9050m\(^2\) = 90500000cm\(^2\)
b, (5 + 20) x y = 525m\(^2\)
=> 25 x y = 525m\(^2\)
=> y = 525m\(^2\) : 25
=> y = 21m\(^2\) = 210000cm\(^2\)