x = 10a; y = 10b; z = 10c; t = 10d; u = 10e
x + y + z + t + u = 10a + 10b + 10c + 10d + 10e = 10 (a + b + c + d + e)
10^2 - (x + y + z + t + u) / (a + b + c + d + e) = 100 - 10 = 90
