Question

A + b = 15, b+ c = 7, c + d = 8, ad + bc -ab - cd = ...

Answer 1

A = 12
b = 3
c= 4
d = 4

ad = a . d
= 12 . 4
= 48
bc = b . c
= 3 . 4
= 12
ab = a . b
= 12 . 3
= 36
cd = c . d
= 4 . 4
= 16

ad + bc - ab - cd = 48 + 12 - 36 - 16
= 8


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