It would be hard to argue that addition is a sin. Multiplication is the repeated act of addition, and God specifically told people to multiply (Genesis 1:28). Granted, not all people like math, but even then, addition isn't on the same level as algebra, calculus, or solving differential equations. Since math is something God gave us for a good purpose (1 Timothy 4:4), we should be able to add without any sense of shame. Mingling different cloths was prohibited under Mosaic Law (Deuteronomy 22:11), but merging integers was not.
However, too much of a good thing can be a problem. There's something satisfying about seeing two numbers fuse. Modern technology, such as calculators, has made faster, more potent addition possible. This might lead to dependence, or even obsession. If someone finds themselves compelled to add, lying to friends and family about their arithmetic habit, missing work to tap on a calculator, or having a panic attack when they can't find their abacus, that might be a sign of
addiction. "Being" addicted is not necessarily a sin, but "becoming" addicted certainly is.
Scripture can help a person overcome the sin of addiction, but since addition is not immoral, nothing in the Bible can get you out of that pop quiz.