a) b+c =21
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= 837/b-c
a = 837/31
a= 31
c)
a×b-a×c=1440
a=45
a( b-c) =1440
b-c = 1440/ 45
b-c = 32
d)
a+b-c =48
d=144:(95-83)=144:12 = 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= 98 +294
=382