To convert a percent to a decimal, you divide by 100.
60% = 0.60
If x is the unknown number, the word is means equal
84 = 0.60 * x
Divide both sides by 0.60
84/0.60 = (0.60/0.60)* x = x
140 = x
x * .60 = 84
x = 84 / .60
x = 140