Need help ASAP. The questions are for 9-11.

Idon’t understand this.. will someone ? will mark brainliest along with 20 points.

To solve the system of equations below, pedro isolated the variable y in the first equation and then substituted it into the second equation. what was the resulting equation? { 5y=10x {x^2+y^2=36

When 142 is added to a number the result is 64 more times the number my options are 35 37 39 41