Skill: Solve one-step addition equations

One-step addition equations represent an unknown addend in a whole-number relationship, such as $x+27=65$, $27+x=65$, or $27+ x=65$; solving means determining the number that makes both sides equal, often by using the inverse relationship between addition and subtraction. The understanding includes interpreting the equal sign as a balance rather than an instruction to compute, and is limited to single-step equations with whole numbers, not negative numbers, fractions, decimals, or multi-step algebraic expressions.