Tobin is solving the equation 3 (x minus 1.25) = 11.25. His work is shown below.

3 (x minus 1.25) = 11.25. 3 x minus 3.75 = 11.25. 3 x minus 3.75 + 3.75 = 11.25 + 3.75. 3 x = 15. 3 x times 3 = 45 times 3. x = 135.