Question

5x - 8y = -9
y + x = 6

3x-y = 7
4x-5y=2

3x+y=-15
2y-3x= 0

x + y = 120
2x + 3y = 50

Answer 1

a) y+x=6
5x - 8y = -9

x=6-y
5(6-y)-8y=-9
30-5y-8y=-9
-13y=-9-30
-13y=-39*(-1)
13y=39
y=39/13
y=3

3+x=6
x=6-3
x=3

b) 3x-y = 7
4x-5y=2


-y=7-3x*(-1)
y=-7+3x
4x-5(-7+3x)
4x+35-15x=2
-11x=-33*(-1)
11x=33
x=33/11
x=3

3*3-y=7
6-y=7
-y=7-6
-y=1*(-1)
y=1

c) 3x+y=-15
2y-3x= 0

y=-15-3x
2(-15-3x)-3x=0
-10-6x-3x=0
-9x=10*(-1)
9x=-10
x=10/9
x=1,11

y=-15-3*1,11
y=-15-3,33
y=11,666

d) x + y = 120
2x + 3y = 50
x=10-y
2(10-y)+3y=50
20-2y+3y=50
y=70

x=10-70
x=-60

espero ter ajudado!!!

Answer 2

$5x - 8y = - 9 \\ y + x = 6 \\ \\ y = 6 - x \\ \\ 5x - 8(6 - x) = - 9 \\ 5x - 48 + 8x = - 9 \\ 13x = 39 \\ x = 3 \\ \\ y = 6 - x \\ y = 6 - 3 \\ y = 3$

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$3x - y = 7 \\ 4 x - 5y = 2 \\ \\ - y = 7 - 3x \times ( - 1) \\ y = - 7 + 3x \\ \\ 4x - 5( - 7 + 3x) = 2 \\ 4x + 35 - 15x = 2 \times ( - 1) \\ 11x = 33 \\ x = 3 \\ \\ y = - 7 + 3x \\ y = - 7 + 9 \\ y = 2$

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$3x + y = - 15 \\ 2y - 3x = 0 \\ \\ - 3x = - 2y \times ( - 1) \\ 3x = 2y \\ \\ 2y + y = - 15 \\ y = - 5 \\ \\ 3x = 2( - 5) \\ x = \frac{ - 10}{3}$

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$x + y = 120 \\ 2x + 3y = 50 \\ \\ x = 120 - y \\ \\ 2(120 - y) + 3y = 50 \\ 240 - 2y + 3y = 50 \\ y = - 190 \\ \\ x = 120 - y \\ x = 120 - ( - 190) \\ x = 310$