"One plus one equals two."
Translation:אחת ועוד אחת שווה שתיים.
There are two Hebrew synonyms that we can use for "equals". One is "שווה" and the second is "הם". "הם" should also be considered as a correct answer.
When counting and in maths, one uses feminine numerals. The distinction between masculine and feminine numerals (i.e. אחת and אחד) is visible when applying numerals to nouns (one combines i.e. masculine noun with masculine numeral). Cheers!