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Positive + Positive = Positive: 5 + 4 = 9Adding Rules:Negative + Negative = Negative: (- 7) + (- 2) = - 9

Sum of a negative and a positive number: Use the sign of the larger number and subtract

(- 7) + 4 = -3

6 + (-9) = - 3

(- 3) + 7 = 4

5 + ( -3) = 2

Negative - Positive = Negative: (- 5) - 3 = -5 + (-3) = -8Subtracting Rules:Positive - Negative = Positive + Positive = Positive: 5 - (-3) = 5 + 3 = 8

Negative - Negative = Negative + Positive = Use the sign of the larger number and subtract

(Change double negatives to a positive)(-5) - (-3) = ( -5) + 3 = -2

(-3) - ( -5) = (-3) + 5 = 2

Positive x Positive = Positive: 3 x 2 = 6Multiplying Rules:Negative x Negative = Positive: (-2) x (-8) = 16

Negative x Positive = Negative: (-3) x 4 = -12

Positive x Negative = Negative: 3 x (-4) = -12

Positive ÷ Positive = Positive: 12 ÷ 3 = 4Dividing Rules:Negative ÷ Negative = Positive: (-12) ÷ (-3) = 4

Negative ÷ Positive = Negative: (-12) ÷ 3 = -4

Positive ÷ Negative = Negative: 12 ÷ (-3) = -4

Now here are some for you to try:

(a) What do x and y equal?

3x + 4y = 10

2x + 5y = 9

(b)What do x and y equal?

3x − 2y = 9

−x + 3y = −3

(c) What do x and y equal?

2x − y = 5

3x + 4y = 2

(d) What do x and t equal?

5x + 7t = 8

7x − 4t = 25

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