Answer:
Since we know what y is, it is 3x+9, we can substitute 3x+9 in for y in the first equation
4x+5y=7
Substitute 3x+9 in
4x+5(3x+9)=7
Distribute the 5
4x+ 5*3x +5*9=7
(4x+15x)+45=7
Combine like terms
19x=-38
Divide both sides by 19
x= -2
Now we know x, and have to find y. Substitute -2 in for x in either of the equations
y=3x+9
y=3(-2)+9
y=-6+9
y=3
Answer:
x= -2, y= 3
Step-by-step explanation:
Solve for the first variable in one of the equations, then substitute the result into the other equation.
