The coupon is applied first, which reduces the cost of the sneakers to 120 - 10 = $<<120-10=110>>110.
Next, the 10% discount leads to a reduction in price of 110*0.1 = $<<110*0.1=11>>11.
Therefore, the final price the man must pay is 110 - 11 = $<<110-11=99>>99.
#### 99