Question

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8Si9

Answer 1

$8)x - y = 12$

$z = 10$

$xz - yz = z(x - y) = 10 \times 12 = 120$

$9)b + c = 14$

$ab + ac = 420$

$a(b + c) = 420$

$14a = 420$

$a = 420 \div 14$

$a = 30$

Answer 2

8. x-y=12, z=10 ⇒ xz-yz=z(x-y)=10x12= 120

9. ab+ac=420, b+c=14 ⇒ a(b+c)=420 ; inlocuim b+c=14, ax14=420 ⇒a=420:14= 30