Salutations!
Mark got 20% raise for his salary. If this salary was $1800 what is the new salary?
So lets solve this!
Mark got 20% "raise" for his salary. It clearly indicates that it is percentage of increase, so therefore, after solving out all the sum, we would be adding up 1800 to get the total of the new salary.
Lets form this into statements ----
Percentage increase = 20%
Mark's old salary = $1800
Mark's new salary = 20 × 1800/100
Cancel out the zeros to make it more logical ----
20 × 18/1
= 360.
Now, we need to add 1800 and 360 to get Mark's new salary
1800 + 360 = $2160.
Mark's new salary is $2160.
Hope I helped :D