15% tip on a bill of $51.03

total = $58.68, tip = $7.65
Explanation: 15% of 51.03 + 51.03. So (15/100)*51.03+51.03= 7.6545 +51.03 = 58.6845. The tip is $7.65 and the final amount is $58.68.
Another way to solve is: 1.15 * 51.03 = 58.6845. This works because (15/100)*51.03+51.03–> 51.03*((15/100)+1) distributive property. For tip only, subtract 51.03 and you get 7.6545

√81/63

Step-by-step explanation:

(9x-18)7x+5= 63x^2-86+5; 63x^2=81;x=√81/63