Answer:
22 m
Step-by-step explanation:
Total distance travelled by marble while falling down = height above surface of lake + depth of lake = 15 + 7 = 22 m
Answer:
81
Step-by-step explanation:
Given the expression: 
To make it a perfect square, we follow the following steps.
Divide the coefficient of x by 2
- Coefficient of x=18, 18/2=9
Square It
Add it to the expression
This is written as a perfect square as: 
The constant term required therefore is 81.

At this point in time, you can use a technique called cross-mutiplication, where you say that

, and

at this point in time, you can devide each side by 8 and solve