Question 1185944
1. **Find James' initial earnings:**
   James' earnings increased by 10% to 7200 kshs. Let his initial earnings be 'x'.
   x + 0.10x = 7200
   1.10x = 7200
   x = 7200 / 1.10
   x ≈ 6545.45 kshs

2. **Find John's initial earnings:**
   The ratio of James' to John's earnings was 4:3.
   John's initial earnings = (3/4) * James' initial earnings
   John's initial earnings = (3/4) * 6545.45
   John's initial earnings ≈ 4909.09 kshs

3. **Find John's new earnings:**
   The sum of their new earnings was 15600 kshs.
   John's new earnings = Total new earnings - James' new earnings
   John's new earnings = 15600 - 7200
   John's new earnings = 8400 kshs

4. **Calculate the percentage increase in John's earnings:**
   Percentage increase = [(New earnings - Initial earnings) / Initial earnings] * 100
   Percentage increase = [(8400 - 4909.09) / 4909.09] * 100
   Percentage increase ≈ 71.1%

Therefore, the percentage increase in John's earnings is approximately $\boxed{71.1\%}$.