Answer:
X = 108.
Step-by-step explanation:
Heights are equal, So equation will be,

So, solving the eq.
Subtract 4 from both sides ,

Divide 3 to both sides,

Squaring both sides,

Add 8 to both sides,

The answer for A is 2,026. I set a porportion up which is 77/x = 3.8/100
The answer to B is 26
The series is 84(1+1/5+1/25+...)=84(1/(1-1/5)=84÷4/5=84×5/4=21×5=105. Upper limit is 105.