The surface area of a cylinder is 2πr² + 2πrh:

sa = 2πr² + 2πrh
sa = 2π(5²) + 2π(5 x 5)
sa = 2π(25) + 2π(25)
sa = (2 x 25)π + (2 x 25)π
sa = 50π + 50π
sa = 100π

A rhombus is a parallelogram with four equal-length sides. A square is a rectangle with four equal-length sides.

The area of a parallelogram is equal to its length x width:

a = l x w
a = a x b
a = 6 x 3
a = 18

The first step to solve a quadratic expression that's not set to zero is to solve the equation so that it is set to zero:

y² - 3 = 5y + 3
y² - 3 - 3 = 5y
y² - 5y - 6 = 0
y² - 5y - 6 = 0

Next, factor the quadratic equation:

y² - 5y - 6 = 0
(y + 1)(y - 6) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (y + 1) or (y - 6) must equal zero:

If (y + 1) = 0, y must equal -1
If (y - 6) = 0, y must equal 6

So the solution is that y = -1 or 6

The perimeter of a triangle is the sum of the lengths of its sides:

p = x + y + z
p = 15cm + 12cm + 9cm = 36cm