step1. find the how much he buy he buy 45
step2. find the % the % is 4 move to decimal left 4% which is .04
step3. multilply the how much he buy or the % so this is that 45*.04=1.8
step4. what are they said they said tax is like add so we got 1.8+$45=46.8
so the answer is 46.8
look at what is the step and you understand the problem more easy way.