If the increase is 120%, you need to find what 120% of 70 is. The best way to work this out is to find 10%, and multiply by 12. To find 10%, you have to divide the answer by 10, therefore, 10% of 70 is 7. In order to find 120%, you have to multiply this by 12, 7x12=84. Therefore, Steve earns $70+ $84 (as he makes 120% more, so this includes the figure from the previous month).
In February, Steve earns $154
Hope this helps :)
