PLEASE PLEASE HELP WITH THIS ITS AN EXAM

Create and solve a linear equation that represents the model, where squares and triangles are shown evenly balanced on a balance beam. assume the weight of a square is 1 unit and the weight of a triangle is unknown.

The perimeter of a triangle is 69 cm. the first is 5 cm shorter than the second side. the third side is twice as long the first side. find the length of each side

Given the equation f(x)=a(b)x where the initial value is 40 and the growth rate is 20% what is f(4)