simultaneous equations Two or more equations that can be manipulated to give common solutions. In the simultaneous equations x+10y = 25 and x+y = 7, the problem is to find values of x and y, such that those values are solutions of both the equations simultaneously. This can be done by subtracting the two equations to give a single equation in y, which can then be solved. Substituting the value of y in either equation gives the value of x.

simultaneous equations A set of equations that together define an unknown set of values or functions. The term is normally applied to linear algebraic equations.