Answer to Question 1:
A way you can prove that the slope (m) = -2 is to write the equation:
3x + 2y + 7 = 5x + 3y + 10 in Slope-intercept form (y=mx+b). So all you need to do is solve for y. You will see that it will be y = -2x - 3. Step-by-step on how to solve it is in the image below. The coefficient of x is the slope (m), which is -2. So, it is proved that the slope is -2.
Question 2: Sorry, I don’t know how to solve for Question 2. But hopfully my answer to Question 1 helps you out :)