Which system of linear equations can be solved using equation {x y}={1/4 3/4 1 2} {28 -12}

What is the first step of an indirect proof of a number that is divisible by two

Offering 30 if a plus b plus c equals 68 and ab plus bc plus ca equals 1121, where a, b, and c are all prime numbers, find the value of abc. the answer is 1978 but i need an explanation on how to get that.

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