I'm not very good at economics so i'm probably wrong but, my method of doing this question would be:
Food = 110 - 100 x 0.3 (CPI weighting as a decimal)
Health = 130 -100 x 0.1
Housing = 125 - 100 x 0.15
Clothing = 120 - 100 x 0.2
and when you do the calculations, clothing comes out to...