Which equation has infinitely many solutions?

Equation C. 5.1 + 2y + 1.2 = -2 + 2y + 8.3

Step-by-step explanation:

Equation C is the only equation in the list in which the terms that contain the unknown "y" on each side of the equal sign are identical, therefore when solving for this unknown and trying to group them on one side, they go away, leaving us with a relationship among numerical values that is always true:

5.1 + 2y + 1.2 = -2 + 2y + 8.3

5.1 + 1.2 = -2 + 8.3

6.3 = 6.3

Then this equation is true for any value of the unknown y, and y- can adopt infinite number of values, independent of which the equation will always be a true statement (giving thus infinite number of solutions).