How many equations are needed to solve for 1 unknown variable?

The number of equation/s that are needed in order to solve the problem is equal to the number of the varying variables involved. In this regard, we would say that to solve for 1 unknown variable, only 1 equation is needed. 

For number of variables greater than 1, as stated above, the number of equations should be equal to that number. However, it has to be noted that the equations should be independent and not the multiplicative of another. 

For the concept of multiplicity,

x + y = 0 and 2x + 2y = 0 are just the same equations. 

Hence, the answer to this item is one (1). 

Step-by-step explanation:

Ok, this problem is on construction in mathematics.

also, see attached a rough sketch of the two constructions.

The similarities, as can be seen, is that for both constructions, we need to two major points to obtain a bisector, for the line segment the major points are (A and B) and for the angle segment the points are(P and Q)

The difference between the two construction is that the line segment needs basically two bisectors to equally divide the line located at (O and P), while the angle segment needs just one bisector at (O) to bisect the angle.