Solve by using substitution . SHOW YOUR WORK. 3х + y = –17
бx — бу = –18

X = —5 and Y = —2

Step-by-step explanation: What we have is a pair of simultaneous equations;

3X + Y = —17 —————-(1)

6X — 6Y = —18 ————(2)

We shall use the substitution method as instructed. Looking at equation (1),

We shall make Y the subject of the equation, hence

Y = —17 —3X

We shall now substitute for the value of Y into equation (2)

6X — 6Y = —18

6X — 6(—17 —3X) = —18

6X + 102 + 18X = —18

By collecting like terms we now have

24X = —18 —102

(Note that when a positive value crosses to the other side of the equation it becomes negative and vice versa)

24X = —120

Divide both sides of the equation by 24

X = —5

Having calculated the value of X as —5, we can now calculate Y as follows

From equation (1)

3X + Y = —17

3(—5) + Y = —17

—15 + Y = —17

Add 15 to both sides of the equation

—15 + 15 + Y = —17 + 15

Y = —2

Therefore, X = —5 and Y = —2