The curry house previously bought 3 peppers per very spicy curry * 30 very spicy curries = <<3*30=90>>90 peppers for very spicy curries.
They also bought 2 peppers per spicy curry * 30 spicy curries = <<2*30=60>>60 peppers for spicy curries.
They also bought 1 pepper per mild curry * 10 mild curries = <<1*10=10>>10 peppers for mild curries.
So they were previously buying 90 + 60 + 10 = <<90+60+10=160>>160 peppers.
They now buy 2 peppers per spicy curry * 15 spicy curries = <<2*15=30>>30 peppers for spicy curries.
They also now buy 1 pepper per mild curry * 90 mild curries = <<1*90=90>>90 peppers for mild curries.
So they now buy 30 + 90 = <<30+90=120>>120 peppers.
This is a difference of 160 peppers bought originally - 120 peppers bought now = <<160-120=40>>40 peppers.
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