Answer:
After substitution, the first step when evaluating X + 3X - 4.2 when X=5, will be:
A. Multiply 3 by 5.
when X=5; X + 3X - 4.2 = 5 + 15 - 4.2
X + 3X - 4.2 = 15.8
Step-by-step explanation:
Because multiplication has priority in addition and subtraction.
