NapkinCalc

Algebra 1

Solving a linear equation

Solve 3x + 5 = 17. Undo the equation from the outside in:

  1. Subtract 5 from both sides → 3x = 12
  2. Divide both sides by 3 → x = 4

The cell below does both steps at once — and the check proves the answer by plugging it back in:

x=17−53x = \frac{17 - 5}{3} = 44 undo +5, then undo ×3
✓ pass abs(3⋅x+5−17)<10−9\mathrm{abs}\left(3 \cdot x + 5 - 17\right) < 10^{-9} plug it back in: 3x + 5 really is 17