A triangle is a three-sided polygon. It has three interior angles that add up to 180° (a + b + c = 180°). An exterior angle of a triangle is equal to the sum of the two interior angles that are opposite (d = b + c). The perimeter of a triangle is equal to the sum of the lengths of its three sides, the height of a triangle is equal to the length from the base to the opposite vertex (angle) and the area equals one-half triangle base x height: a = ½ base x height.

You need to find the value of b so solve the first equation in terms of y:

-5b + y = -2
y = -2 + 5b

then substitute the result (-2 - -5b) into the second equation:

9b + 7(-2 + 5b) = 4
9b + (7 x -2) + (7 x 5b) = 4
9b - 14 + 35b = 4
9b + 35b = 4 + 14
44b = 18
b = \( \frac{18}{44} \)
b = \(\frac{9}{22}\)

The area of a trapezoid is one-half the sum of the lengths of the parallel sides multiplied by the height:

a = ½(b + d)(h)
a = ½(7 + 3)(4)
a = ½(10)(4)
a = ½(40) = \( \frac{40}{2} \)
a = 20

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

sa = 2πr² + 2πrh
sa = 2π(1²) + 2π(1 x 5)
sa = 2π(1) + 2π(5)
sa = (2 x 1)π + (2 x 5)π
sa = 2π + 10π
sa = 12π

The formula for circumference is circle diameter x π:

c = πd
c = 17π