To multiply monomials, multiply the coefficients (the numbers that come before the variables) of each term, add the exponents of like variables, and multiply the different variables together.

(2a)(5ab) + (7a²)(7b)
(2 x 5)(a x a x b) + (7 x 7)(a² x b)
(10)(a¹⁺¹ x b) + (49)(a²b)
10a²b + 49a²b
59a²b

To solve this equation, isolate the variable for which you are solving (c) on one side of the equation and put everything else on the other side.

7c - x = -8c - 4x + 1
7c = -8c - 4x + 1 + x
7c + 8c = -4x + 1 + x
15c = -3x + 1
c = \( \frac{-3x + 1}{15} \)
c = \( \frac{-3x}{15} \) + \( \frac{1}{15} \)
c = -\(\frac{1}{5}\)x + \(\frac{1}{15}\)

The area of a triangle is equal to ½ base x height:

a = ½bh
a = ½ x 5 x 4 = \( \frac{20}{2} \) = 10

A parallelogram is a quadrilateral with two sets of parallel sides. Opposite sides (a = c, b = d) and angles (red = red, blue = blue) are equal. The area of a parallelogram is base x height and the perimeter is the sum of the lengths of all sides (a + b + c + d).

The formula for circumference is circle diameter x π. Circle diameter is 2 x radius:

c = πd
c = π(2 * r)
c = π(2 * 18)
c = 36π