Substituting y=3 in 4x-5y=-12 we get:
[tex]4x-5\cdot3=-12.[/tex]Simplifying the above equation we get:
[tex]4x-15=-12.[/tex]Adding 15 to the above equation we get:
[tex]\begin{gathered} 4x-15+15=-12+15, \\ 4x=3. \end{gathered}[/tex]Finally, dividing the above equation by 4 we get:
[tex]\begin{gathered} \frac{4x}{4}=\frac{3}{4}, \\ x=\frac{3}{4}\text{.} \end{gathered}[/tex]Answer: If 4x-5y=-12 and y=3 then:
[tex]x=\frac{3}{4}\text{.}[/tex]