I will show you with other numbers. Salman had 1000 tulips the first year. In the third year, he had 1400 tulips, so his percentage increase was (1400 - 1000) / 1000 = 40% over that time.
When working out percentage increase or decrease, you put the original (earlier) value in the denominator and the numerator is the later value minus the earlier value.
Another example: Monisha had 80 students in her class, but she was a strict professor and a month later she only had 65 students still in her class. That percentage change is (65 - 80) / 80 = -18.75%, which you would call a percentage decrease of 18.75%.
Hope this helps,
Stephen La Rocque.