-1 1/2 + 5 7/8 =

-1 1/2 + 5 7/8 = ?

$\begin{array}{rcl} -1 \frac12 + 5 \frac78 \\ &=& - 1 - \frac12 + 5+\frac78 \qquad | \qquad \frac78 = \frac{4+3}{8} = \frac48+\frac38 = \frac12+\frac38\\ &=& - 1 - \frac12 + 5+\frac12+\frac38\\ &=& - 1 + 5+\frac38\\ &=& 4+\frac38\\ &=& 4\frac38\\ \mathbf{-1 \frac12 + 5 \frac78 } & \mathbf{=} & \mathbf{4\frac38}\\ \end{array}$