## Elementary Technical Mathematics

$3x+y=7$ $4x-y=0$ $\longrightarrow$ solve for y by adding y to both sides $4x-y+y=0+y$ $4x=y$ Substitute 4x for y in the first equation. $3x+4x=7$ $\longrightarrow$ simplify $7x=7$ $\longrightarrow$ divide both sides by 7 $7x\div7=7\div7$ $\longrightarrow$ simplify $x=1$ Substitute 1 for x in the second equation. $4(1)-y=0$ $\longrightarrow$ simplify and add y to both sides $4-y+y=0+y$ $\longrightarrow$ simplify $4=y$