x - tenths digit
y - units digit
[tex]10x+y=4(x+y)\\
10x+y=2xy\\\\
10x+y=4x+4y\\
10x+y=2xy\\\\
6x=3y\\
10x+y=2xy\\\\
3x=y\\
10x+y=2xy\\\\
10x+3x=2x\cdot3x\\
13x=6x^2\\
6x^2-12x=0\\
6x(x-2)=0\\
x=0 \vee x=2\\\\
y=3\cdot2\\
y=6\\\\
10\cdot2+6=\boxed{26}[/tex]
