## Elementary Technical Mathematics

$4x+5y=10$ $4x=-10y$ Using the value given in the second equaion, substitute -10y for 4x in the first equation. $-10y+5y=10$ $\longrightarrow$ simplify $-5y=10$ $\longrightarrow$ divide both sides by -5 $-5y\div-5=10\div-5$ $\longrightarrow$ simplify $y=-2$ Substitute -2 for y in the second equation. $4x=-10(-2)$ $\longrightarrow$ multiply $4x=20\longrightarrow$ divide each side by 4 $4x\div4=20\div4$ $\longrightarrow$ divide $x=5$