given a+1=b+2=c+3=d+4=a+b+c+d+5 the value of a+b+c+d is dengan cara

a + 1 = b + 2 = c + 3 = d + 4 = a + b + c + d + 5

Misalkan : (a + 1) = x
(a + 1) + (b + 2) + (c + 3) + (d + 4) = 4x
x = a + 1 , a + 1 sama dgn a + b + c + d + 5

a + b + c + d + 10 = 4(a + b + c + d + 5)
a + b + c + d + 10 = 4a + 4b + 4c + 4d + 20
a + b + c + d + 10 = 4(a + b + c + d) + 20
Pindah pindah ruas
10 - 20 = 4(a + b + c + d) - (a + b + c + d)
-10 = 3(a + b + c + d)

a + b + c + d = - 10/3