Answer:
Step-by-step explanation:
Given that f(x) = 3x + 21
Plug in 3 for x
F(3)= 3(3) +21
F(3) = 9+21
f(3) = 30
Plug in 7 for x
F(7)= 3(7) +21
F(7) = 21+21
f(7) = 42
144+64= 178

a^2+b^2= c^2
Whenever finding a missing length use the formula up above :
a^2+b^2= c^2
a^2-b^2= c^2
144-64= 80

Answers are 13.3 and 8.9
Nice and simple. PEMDAS. Parentheses, exponents, multiple, division, addiction, subtraction.
The first thing you do is solve the numbers in the parenthesis, which would turn to
(312) + (714) = 1026