Solving x + 5 = 12

Pre-Algebra · Axiom Academy

Solve a one-step equation by isolating the variable, using the balance-scale idea and an inverse operation. Solve for x in the equation x + 5 = 12 . Think of the equation as a balanced scale: whatever is on the left weighs the same as the right. Nice work — you solved a one-step equation by isolating the variable. Remember these ideas: Balance-scale principle: an equation is a balanced scale — whatever you do to one side, you do to the other. Goal: isolate the variable, getting x alone on one side. Inverse operations: undo addition with subtraction (and subtraction with addition). Result: x + 5 = 12 gives x = 7 , since 12 - 5 = 7 . The same subtract-from-both-sides move solves any one-step addition equation — just change the numbers.

This is the written version of the interactive lesson above. See the full Pre-Algebra course.