To solve this equation, we can follow these steps:

Distribute the 2x on the left side of the equation:
2x x - 2x 7 = 3x - 21
2x^2 - 14x = 3x - 21

Move all terms to one side of the equation by subtracting 3x from both sides:
2x^2 - 14x - 3x = -21
2x^2 - 17x = -21

Set the equation equal to 0:
2x^2 - 17x + 21 = 0

Factor the quadratic equation:
We can factor 2x^2 - 17x + 21 by finding two numbers that multiply to 42 (2*21) and add to -17. The numbers are -14 and -3.
(2x - 3)(x - 7) = 0

Set each factor to 0 and solve for x:
2x - 3 = 0
2x = 3
x = 3/2

and

x - 7 = 0
x = 7

Therefore, the solutions to the equation are x = 3/2 and x = 7.