"Analog computers" were used years ago for solving problems, starting around WW II, including differential equations.
Multiplication and division required external analog components, and logarithms could use semiconductor diodes.
Besides addition and subtraction, the technique works well for differentiation and integration (in calculus) continuously, rather than in small finite steps.
Googling "analog computer" should give you a host of references for that topic, which is the original use for operational amplifiers, and the reason for that name.