Question 658091
Seperate [sic] 90 into two parts such that the second part is 30 less than twice the first part.

I have figured that: 
x = the first part
y = the second part
i think that
90=2x-30+y is the equation but i dont know where to go from there, i have to use either substitution or elimination.
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x + y = 90
y = 2x - 30
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x + 2x-30 = 90
x = 40
y = 50