Question

Find the solution of this system equations.
x-7y=-20 and -3x+9y-36

Helpp?

Answer 1

do you prefer substitution or elimination ?

Answer 2

I have no i idea.. The question only says what it says above.. I really don't understand Math at all. :/

Answer 3

lets try substitution because it is a little easier.
x - 7y = -20 --> x = 7y - 20
now sub 7y - 20 in for x in the other equation
-3x + 9y = -36
-3(7y - 20) + 9y = -36 -- distribute through the parenthesis
-21y + 60 + 9y = -36 -- subtract 60 from both sides
-21y + 9y = -36 - 60 -- combine like terms
- 11y = -96 -- divide by -11
y = -96/-11
y = 96/11
now sub 96/11 in for y in either of the equations
x - 7y = -20
x - 7(96/11) = -20
x - 672/11 = -20
x = -20 + 672/11
x = - 220/11 + 672/11
x = 452/11
check...
x - 7y = -20
452/11 - 7(96/11) = -20
452/11 - 672/11 = -20
-220/11 = -20
-20 = -20 (correct)

x = 452/11 and y = 96/11

sorry it took so long, I had a little trouble

Answer 4

It's fine. Thank you! (: