The equation is m + 21 = 60.

Apply subtraction property of equality: Subtract 21 from each side.

m + 21 21 = 60 21

m + 0 = 60 21              (Apply additive inverse property: 2424 = 0)

m  = 6021                    (Apply additive identity property: x + 0 = x)

m = 39                             (Subtract: 6021 = 39)

Check:

To check the solution, substitute m = 39 in original equation.

m + 21 = 60 39 + 21 = 60

60 = 60                            (Add: 39 + 21 = 60)

The statement is true.

Graph the solution on number line.

\
• First draw a number line.
\
• Mark a dot at 39 on  the number line.
\

The value of m = 39.