simultaneous equations 
plural noun
Equations involving two or more unknowns that are to have the same values in each equation.We solve numerically a system of two simultaneous equations, with two unknowns, as follows....
- Because the issue is not how the simultaneous equations, partial derivatives or matrices are manipulated, but what the symbols in the various equations purport to represent.
- The simultaneous equations suggested in Equation 2 and developed at each road section were used to study the variation in PCU with influencing parameters.