Answer: He pays x*0.642
Step-by-step explanation:
Suppose that we have an object with an initial price P.
If we have a discount of X%, then the new price will be:
NP = P*(1 - X%/100%)
And if we have an increase of X%, the new price is:
NP = P*(1 + X%/100%)
In this case, we have an initial item that costs x dollars, first we have a coupon for 40% off, then we have a discount of 40%.
Then the new price is:
NP = x*(1 - 40%/100%) = x*(1 - 0.4) = x*0.6
Now we add a tax of the 7%, then the final price will be:
FP = (x*0.6)*(1 + 7%/100%) = (x*0.6)*(1 + 0.07) = x*(0.6*1.07) = x*0.642
This is the total amount he pays at the register.