Solve the problem and win prizes !!!

Day 3,392, 02:05 Published in Iran Iran by Mc Awesome
Solve the following problem and win Prizes !!
First person to guess it right will win 25 Q4 weapons
Second person will win 20 Q4 weapons
Third person will win 15 Q4 weapons
Fourth person will win 10 Q4 weapons
Fifth person will win 5 Q4 weapons


1 + 5 = 18
2 + 10 = 36
3 + 15 = 54
4 + 20 = ?
What is the "?"



Article #E0003