In the first 3 months, expenditure is 72%.

=> in the first 3 months her saving is (100-72)% = 28%.

In next 4 month, she increased her saving by 25%

which is equal to (28 + 28*25/100)% = 35%

There forre in next four months her expenditure is (100-35)% = 65 %.

There for the % average expenditure in 7 months = (72.3+65.4)/7 %

= 476/7 =Her average expenditure = $(1800 . 68)/100 =68%

$1224