74. Points $A(x ; 3)$ and $B(-5 ; y)$ belong to the line given by the equation $7 x+2 y=41$. Find the unknown coordinates of the points.
Solution. Since points $A$ and $B$ belong to the given line, their coordinates satisfy the equation of this line. Substituting the known coordinates into this equation, we get an equation with one unknown:

$$
\begin{gathered}
A(x ; 3) ; 7 x+2 \cdot 3=41 ; 7 x=35 ; x=5, \text { i.e. } A(5 ; 3) \\
B(-5 ; y) ; 7 \cdot(-5)+2 y=41 ; 2 y=76 ; y=38, \text { i.e. } B(-5 ; 38) .
\end{gathered}
$$