Not sure about Japan but in Poland the variables in problems are either symbolic and you solve it symbolically, or if they are given as values then they are usually chosen just right to not make arithmetic much of a bother (that actually results in a fun 'sanity check' that if you start getting something waaay crazier than 'normal' you double check if you didn't screw something up somewhere along the way or if there is a better way to solve it).

But everyone is taught to only substitute variables for values at the very, very end so calculators are not needed at all. At some point in education there is no point in testing arithmetic skills over and over again, the problems and the methods of finding out solutions to them are what matters