Step-by-step explanation:
a. we simply subtract 3. from 2.
x + 2y + z = 15
- -3x + y + z = 2
--------------------------
4x + y 0 = 13
b. we multiply 3. by 3 and then subtract from 1.
2x - 4y + 3z = -7
- -9x + 3y + 3z = 6
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11x - 7y 0 = -13
c. we multiply the result of a. by 7, and then simply add a. and b., because the y terms have different signs already.
28x + 7y = 91
+ 11x - 7y = -13
--------------------------
39x 0 = 78
39x = 78
x = 2
d. we use this x = 2 in the result of a.
4×2 + y = 13
8 + y = 13
y = 5
e. using x = 2 and y = 5 in 2.
2 + 2×5 + z = 15
2 + 10 + z = 15
12 + z = 15
z = 3
the solution is therefore (2, 5, 3).
