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

sa = 2πr² + 2πrh
sa = 2π(2²) + 2π(2 x 5)
sa = 2π(4) + 2π(10)
sa = (2 x 4)π + (2 x 10)π
sa = 8π + 20π
sa = 28π

An exterior angle of a triangle is equal to the sum of the two interior angles that are opposite:

d° = b° + c°

To find angle c, remember that the sum of the interior angles of a triangle is 180°:

180° = a° + b° + c°
c° = 180° - a° - b°
c° = 180° - 60° - 53° = 67°

So, d° = 53° + 67° = 120°

A shortcut to get this answer is to remember that angles around a line add up to 180°:

a° + d° = 180°
d° = 180° - a°
d° = 180° - 60° = 120°

The sum of the interior angles of a triangle is 180°:
180° = a° + b° + c°
c° = 180° - a° - b°
c° = 180° - 60° - 49° = 71°

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:

x² - 2x - 25 = -5x + 3
x² - 2x - 25 - 3 = -5x
x² - 2x + 5x - 28 = 0
x² + 3x - 28 = 0

Next, factor the quadratic equation:

x² + 3x - 28 = 0
(x - 4)(x + 7) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (x - 4) or (x + 7) must equal zero:

If (x - 4) = 0, x must equal 4
If (x + 7) = 0, x must equal -7

So the solution is that x = 4 or -7

Perimeter is equal to the sum of the four sides:

p = a + b + c + d
p = 6 + 7 + 3 + 5
p = 21