Well, without any prices, I can’t give you a number. And someone else may have a simpler way to do this.
But we’ll call the original bill x.
After the 10% off coupon, the bill is 0.9x
Adding tax = 0.07(0.9x) + 0.9x
Adding a tip = 0.20[0.07(0.9x) + 0.9x)]
If you have numbers to plug in, put them in a comment below & I’ll help more.