Well I added the numbers for 1993, (720+246 = 966) to get the total number of claims for that year.

It is a 15% increase on the previous year (1992) - so 966/115 (which is 115%) = 8.4 (which is 1% of 1992) then multiply that by 100 to get the number of claims made in 1992. (840)

Then simply add the two figures for 1997 (428 + 547 = 975) to get the total for 1997 them just minus 1992 from that.

975 - 840 = 135