a) b + c = 21 si a = 7
a × b + a × c = a × ( b + c ) = 7 × 21 = 147
b) b - c = 31
a × b - a × c = 837
a × ( b - c ) = 837
a × 31 = 837
a = 837 : 31
a = 27
c) a = 45
a × b - a × c = 1 440
a × ( b - c ) = 1 440
45 × ( b - c ) = 1 440
b - c = 1 440 : 45
b - c = 32
d)
a + b - c = 48 si d = 144 : 12 ⇒ d = 12
a × d + b × d - c × d =
= d × ( a + b - c ) =
= 12 × 48 =
= 576
e)
b - c = 7; a = 14; b = 21
a × ( b - c ) + a × b =
= 14 × 7 + 14 × 21
= 14 × ( 7 + 21 )
= 14 × 28 =
= 392
