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

p = x + y + z
p = 7cm + 5cm + 5cm = 17cm

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.

(9a)(9ab) + (8a²)(4b)
(9 x 9)(a x a x b) + (8 x 4)(a² x b)
(81)(a¹⁺¹ x b) + (32)(a²b)
81a²b + 32a²b
113a²b

To combine like terms, add or subtract the coefficients (the numbers that come before the variables) of terms that have the same variable raised to the same exponent.

9a - 5a = 4a

To solve this equation, repeatedly do the same thing to both sides of the equation until the variable is isolated on one side of the < sign and the answer on the other.

8c - 8 < \( \frac{c}{4} \)
4 x (8c - 8) < c
(4 x 8c) + (4 x -8) < c
32c - 32 < c
32c - 32 - c < 0
32c - c < 32
31c < 32
c < \( \frac{32}{31} \)
c < 1\(\frac{1}{31}\)

Perimeter is equal to the sum of the four sides:

p = a + b + c + d
p = 4 + 4 + 9 + 7
p = 24