How do you solve #-20x+7y=137, 4x+5y=43#?

1 Answer
May 19, 2018

Answer:

#x=-3#
#y= 11#

Explanation:

you have 2 equations and 2 unknowns so let's solve by elimination:

#-20x+7y = 137#
#" "4x+5y=43#

#-20x and 4x " have a common denominator "20x# so multiply the bottom equation by 5:

#-20x+7y = 137#
#5(4x+5y=43)#

#-20x+7y = 137#
#" "20x+25y=215#

now add the equations together, notice the x terms cancel:

#32y = 352#

#y= 11#

finally insert y's value in to either of the original equations to solve for x:

#4x+5y=43#

#4x+5(11)=43#

#4x+55=43#

#4x=-12#

#x=-3#