The answer is 12, Good luck!
Start with expression 
1. Separate terms - with x leave in left side, without x write in right side:

2. Divide the last expression by a (
):

Answer: this statement is true when
.
Answer:
1,75 m
Step-by-step explanation:
The radius is by definition half of the diameter and so the half of 3.5 m is 1.75 m