Final answer:
The solutions are: x = 3, y = -2 and x = -3, y = 10.
Step-by-step explanation:
To solve the system of equations xy + 3x = 3 and 3x + y = 7, we can use the method of substitution. 
Step 1: Solve one of the equations for one variable. 
From the second equation, we can isolate y: 
y = 7 - 3x 
Step 2: Substitute the expression for y in the other equation. 
Substituting y = 7 - 3x into the first equation gives: 
xy + 3x = 3 
x(7 - 3x) + 3x = 3 
 7x - 3x^2 + 3x = 3 
-3x^2 + 10x - 3 = 0 
Step 3: Solve the resulting quadratic equation. 
We can use factoring, completing the square, or the quadratic formula to solve the quadratic equation. In this case, let's use the quadratic formula. 
x = (-b ± √(b^2 - 4ac)) / (2a) 
 Plugging in the values, we get: 
x = (-10 ± √(10^2 - 4(-3)(-3))) / (2(-3)) 
x = (-10 ± √(100 - 36)) / (-6) 
x = (-10 ± √64) / (-6) 
 x = (-10 ± 8) / (-6)
Step 4: Calculate the values of x and y. 
Plugging the values of x into the equation y = 7 - 3x, we get: 
For x = (-10 + 8) / (-6), y = 7 - 3((-10 + 8) / (-6)) 
For x = (-10 - 8) / (-6), y = 7 - 3((-10 - 8) / (-6)) 
The solutions are: 
x = 3, y = -2 
x = -3, y = 10