Given a+b+c+d=45

Question

and a+2=b-2=2c=d/2

compute a+b+c-d

Answer 1

a=d/2-2
b=d/2+2
c=d/4 --> a+b+c+d=2d+d/4=45-->d=20
a+b+c-d=d/4=5