## Elementary Technical Mathematics

$7x+8y+93=0$ $y=3x$ Substitute 3x for y in the first equation. $7x+8(3x)+93=0\longrightarrow$ simplify $7x+24x+93=0\longrightarrow$ simplify $31x+93=0\longrightarrow$ subtract 93 from both sides $31x+93-93=0-93\longrightarrow$ simplify $31x=-93\longrightarrow$ divide both sides by 31 $31x\div31=-93\div31\longrightarrow$ simplify $x=-3$ Substitute -3 for x in the second equation. $y=3(-3)\longrightarrow$ simplify $y=-9$