Someone please help us probabilities

3.4a=57.8 what is the the value of a

Ineed to know the ordered pairs for this equation i need the answer quick because it’s a timed test

50 will mark show all use the linear combination method to solve the system of equations. explain each step of your solution. if steps are not explained, you will not receive credit for that step. 2x+9y= -26 -3x-7y=13