how do you use the substitution method for 5x+3y=7 and y=x-3

Question

anonymous · Answer

You know y=x+3 so put x-3 in for y in the other equations and solve for x

5x+3(x-3)=7

then use x to solve for y

anonymous · Answer

x-3*****

anonymous · Answer

ok, so after you write 5x+3(x-3)=7 then what do you do from there?

lilg132 · Answer

you replace y with the equation given so

5x + 3y =7

y = x - 3

so it will now be

5x + 3(x - 3) = 7

expand it

5x + 3x - 9 = 7

bring the numbers to one side and letters on the other

5x + 3x = 7 + 9

8x = 16

now divide 8x by 8 to get x on its own but you have to do it to both sides

8x / 8 = 16 / 8

x = 2

lilg132 · Answer

now we know what the value of x is we can work out y

5x + 3y =7

so

5(2) + 3y = 7

expand the bracket

10 + 3y = 7

now move numbers to one side and letters to the other

3y = 7 - 10

3y = -3

divide both sides by 3 to get y on its own

3y / 3 = -3 / 3

y = -1

DONT FORGET TO CLICK BEST RESPONSE =)

anonymous · Answer

ok thanks so much! ok so i have a couple more i might need help with....so how bout 3x+2y=11 and x+y=4?

anonymous · Answer

can someone please help!