Answer:

» substitute y in eqn(a) with y in eqn(b)

» Find y in eqn(b)

$74.68
10 percent of $124.46 is $12.446 when you multiply that by 4 you get $49.784 then you just have to subtract
$124.46
- 49.784
_________
and you get your answer
<em>To solve for a variable, you have to isolate that variable onto one side.</em>
<h3>1.</h3>
Firstly, multiply both sides by 2: 
Next, divide both sides by a + b and <u>your answer will be:
</u>
<h3>2.</h3>
For this, divide both sides by πr², and <u>your answer will be
</u>
<h3>3.</h3>
Firstly, subtract both sides by 2πr²: 
Lastly, divide both sides by 2πr, and <u>your answer will be:
</u>