Example 1: basic expression, one variable. Find the value of 3b + 4 when b = 10. Here b = 10 so we substitute the b in 3b + 4 for 10. 3×10+4 3 × 10 + 4. Remember that 3b means 3 b. 2 We can now work out the value of the expression: 3×10+4
Example 2: Solve by substitution $$ \begin{aligned} 2x + 5y &= 12 \\ 4x - y &= 2 \end{aligned} $$ Solution: Step 1: Solve one of the equations for either x = or y =. Since the coefficient of y in