Set up an equation, where n is the original number. Since there is a 40% increase, 40% of itself is added to itself to make 14:
n + .4n = 14
You can now combine the n and .4n, since they're compatible terms. Keep in mind that n = 1n:
1.4n = 14
Divide each side by 1.4 to solve for n:
n = 10
The original number is 10.