A rectangle has the dimensions x and x+5.
It's area is 84cm^2. solve for x show working.
I know that x is 7 but. I don't know how to show it tips please`?

Area of rectangle = Length x Breadth

Just replace in the equation. Area = 84, length = x, breadth = x+5
[OR A = 84, L = x+5, B = x].

Plug in the values and solve. Post back if you still have difficulties.