Bananas on sale for $0.40 a pound in you have a coupon for $0.25 off your total purchase write a function rule

0.4b - 0.25 = t

Each banana costs 40 cents when you have a coupon for 25 cents off. So, you subtract 25 cents from the total cost of the bananas when they’re on sale, which is why we subtract it from the cost of 0.4b (bananas) to find the total cost (t) of the (b) amount of bananas.
0.4 = 0.40