[tex]3x+2y=7 \\
x-4y=-21 \\ \\
\hbox{solve the second equation for x:} \\
x-4y=-21 \\
x=4y-21 \\ \\
\hbox{substitute 4y-21 for x in the first equation:} \\
3(4y-21)+2y=7 \\
12y-63+2y=7 \\
14y=7+63 \\
14y=70 \\
y=\frac{70}{14} \\
y=5 \\ \\
x=4y-21=4 \times 5-21=20-21=-1 \\ \\
\boxed{(x,y)=(-1,5)}[/tex]
