Which steps are needed to solve this equation? . b minus 21 = 177 Subtract 21 from the left side and add 21 to the right side of the equation. The answer is b = 198. Check the solution by substituting 198 for b. Add 21 to the left side and subtract 21 from the right side of the equation. The answer is b = 156. Check the solution by substituting 198 for b. Subtract 21 from both sides of the equation. The answer is b = 156. Check the solution by substituting 156 for b. Add 21 to both sides of the equation. The answer is b = 198. Check the solution by substituting 198 for b.