Are the equations -2x=10 and -5x=25 equivalent

To equations are equivalent if and only if they have the same solution set.

Solve for both of the equations.

-2x = 10
x = -5 <-- Divide both sides by -2

-5x = 25
x = -5 <-- Divide both sides by -5

Both have the solution -5.

So, yes both are equivalent.