When three times a number is subtracted from 20, the result is 4 plus the number. What is the number? equation. 20 - 3n= 4 +n (Type an integer or a decimal.) Next, solve the equation. Begin by isolating the constants on one side of the equation and the variables on the other. To move the variables to the right side of the equation, add 3n to both sides. 20-3n = 4+n