Question

Given that X base 7 - 2043 base 7 = 4455 base 7. What is X?

A 7531
B 7431
C 6431
D 6531​

Answer 1

x ₇ - 2043₇ = 4455₇

x ₇ = 2043₇ + 4455₇

In the 7⁰-digits place,

5 + 3 = 8 = 7 + 1 = 11₇

Carry the 1. Then in the 7¹-digits place,

4 + 5 + 1 = 10 = 13₇

Carry the 1. In the 7²-digits place,

0 + 4 + 1 = 5₇

No carrying needed here. Finally,

2 + 4 = 6₇

So we have

x ₇ = 6531₇