Answer:
Value of given expression is 6434.5532 and number of significant figures is 8.
Step-by-step explanation:
The given expression is

We need to find the value of given expression.
On simplifying the parentheses we get

On multiplication we get

Therefore, the value of given expression is 6434.5532 and number of significant figures is 8.
First one the answer is A; Alexander needs 70 ft
8x - 15 = 3x
+15 +15
8x = 3x + 15
-3x
5x = 15
/5 /5
x = 3