solve by substitution?

Question

1.)
-2x+5y=-2
x - 3y=3

2.) a bookstore took in $ 167 on the sale of 5 copies of a new cookbook and 3 copies of a new novel. The next day it took in $ 89 of 3 copies of the cookbook and 1 copy of the novel. what was the price of each book?

for 1.) i got (27,8)
for 2.) i got cookbook= 25 and novel= 14

please check my answers for this quiz

Answer 1

1) -2x + 5y = -2
x - 3y = 3
x = 3 + 3y

-2(3 + 3y) + 5y = -2
-6 - 6y + 5y = -2
-6 - y = -2
6 + y = 2
y = -4
x = 3 + 3(-4)
x = -9

2)
5c + 3n = 167
3c + n = 89
n = 89 - 3c

5c + 3(89 - 3c) = 167
5c + 267 - 9c = 167
-4c = -100
c = 25

n = 89 - 3(25)
n = 14


You were wrong on 1 and right on 2

Answer 2

-2x + 5y = -2
x - 3y = 3

x - 3y = 3
x = 3y + 3

-2(3y + 3) + 5y = -2
-6y - 6 + 5y = -2
-y - 6 = -2
-y = 4
y = -4

x = 3(-4) + 3
x = -12 + 3
x = -9

x = -9
y = -4

www.quickmath.com will give you the same answer.

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5x + 3y = 167
3x + y = 89

3x + y = 89
y = -3x + 89

5x + 3(-3x + 89) = 167
5x - 9x + 267 = 167
-4x = -100
x = 25

y = -3(25) + 89
y = -75 + 89
y = 14

ANS : 25 cookbooks and 14 novels

First ones wrong, second ones right.

Answer 3

x-3y=3
x=3+3y
-2(3+3y)+5y=-2
-6-y=-2
-y=4
y=-4
x-3(-4)=3
x=-9
the S.S.=(-9,-4)

2.5C+3N=167
3C+1N=89
N=89-3C
5C+3(89-3C)=167
-4c=-100
C=25
substituting
N=89-75=14

you are absolutely right on only one count