What is the solution to the system of equations #x+y = 90# and #y = 9x - 10#?

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Answer 1 · 2016-01-28T12:14:14

#x=10,y=80#

#x+y=90#

#y=9x-10#

Clearly in the second equation they have given the value of #y#.
So,substitute the value to the first equation.

#rarrx+(9x-10)=90#

#rarrx+9x-10=90#

#rarr10x-10=90#

#rarr10x=90+10#

#rarr10x=100#

#rarrx=100/10=10#

Substitute the value of #x# to the first equation itself

#rarr10+y=90#

#rarry=90-10=80#

So, #(x,y)=(10,80)#