How do you solve this system of equations by substitution: - x+y = 40 and y = 9x?

2 Answers
Dec 10, 2017

x=5 and y= 45

Explanation:

- x+y = 40 ----- let this be equation (1)and
y = 9x ------be equation (2)

Substitute value of y from equation(2) in equation(1):

(1) => -x + (9x) = 40

=> 8x = 40

=> x=40/8 =5

Now substitute this value of x in equation(2) :

=> y= 9x =9xx5 =45

therefore x=5 and y= 45

Dec 10, 2017

x,y)to(5,45)

Explanation:

-x+y=40to(1)

y=9xto(2)

color(blue)"substitute "y=9x" into equation "(1)

-x+9x=40

rArr8x=40

"divide both sides by 8"

(cancel(8) x)/cancel(8)=40/8

rArrx=5

"substitute this value into equation "(2)

y=9xx5=45

rArr"point of intersection "=(5,45)