People are mixing "solving arithmetic problems" with "solving arithmetic problems without paper or calculator". Furthermore, GP's example mixes "can't calculate

People are mixing "solving arithmetic problems" with "solving arithmetic problems without paper or calculator". Furthermore, GP's example mixes "can't calculate price per pound" with "Can't read a line graph". The former is okay, the more I advance in graduate training as a mathematician, the less I'm able to do mental math. The latter is bad. There are good reasons for teaching mental math to children, but for adults, really, calculators exist. If you can't calculate price-per-pound with a calculator, you have a low IQ (can't translate a simple written instruction to pressing buttons on your phone) and should be elligible for government aid. But if you can't calculate discounts, compound interest, read graphs, etc -- these can be taught. Should be taught. For example: banks could condition debt renegotiations to attendance to special financial education classes for adults. Governments could incentivize banks to do so by picking up part of the check for reduced debt.