Step-by-step explanation:
-The first equation has a unique solution where we must find only the value of Y
-The second equation only has a single solution where we must find the value for the variable q
-In the third equation we can solve it in different ways for when the equation is equal to 7 we can use any mathematical method of equalization, reduction or substitution.
-The fourth equation only has a single solution where we can use the matching method to find the value of p
So the answer is the third option.