They both can be solved using the property of equality of addition or subtraction, that is the same quantity can be added or subtracted from each side of the equality or inequality. The same applies to division and multiplication, but only if the multiplier/divisor is positive. For equalities, it doesn’t matter whether the multiplier/divisor is positive or negative; but for inequalities negative quantities reverse the inequality.
Also if a=b, then b=a. But if the quantities are swapped in an inequality, the inequality is reversed. For example, if a>b then b<a.