a rectangle has a perimeter of 22cm and an area of 30 cubic meter. what are its dimensions?

Answer 1

area is measured in square metres, not cubic metres.
If that is what you meant ....

length ---x
width ---y
2x + 2y = 22
x+y = 11 ---> y = 11-x

xy = 30
x(11-x) = 30
11x - x^2 - 30 = 0
x^2 - 11x + 30 = 0

solve for x, it factors very nicely.