3.3 Lösning 1c

$$\begin{array}{cccccrl} 2 & \cdot & (x\,+\,1) & = & 40 & \quad & {\rm Täck\;över\;} (x\,+\,1) \\ 2 & \cdot & \boxed{(x\,+\,1)} & = & 40 & & \\ 2 & \cdot & \boxed{\quad\;\;?\quad\;\;} & = & 40 & & \\ 2 & \cdot & \boxed{\quad\;20\quad\;} & = & 40 & & \end{array}$$

$$\qquad \Downarrow$$

$$\begin{array}{rclcl} (x\,+\,1) & = & 20 & & \\ x\,+\,1 & = & 20 & \quad & {\rm Täck\;över\;} x \\ \boxed{x}\,+\,1 & = & 20 & & \\ \boxed{?}\,+\,1 & = & 20 & & \\ \boxed{19}\,+\,1 & = & 20 & & \end{array}$$

$\qquad \Downarrow$

$\;\;\; x \; = \; 19$