Question

a+b+c+ab+bc+ca+abc=1000 then (a+b+c)(20)=?

Answer 1

560

Resolve it into (1+a)(1+b)(1+c)=1001

Answer 2

Adding one on both side
a + b + c + ab + bc +ac + abc +1 = 2000 + 1
Using identity
(a + b + c + ab + bc + ac +abc + 1) =  
(1+ a) (1+ b) (1+c)