He didn’t follow PEMDAS which is the an acronym for the order of operations. according to pemdas the first step is parenthesis (which is the p in pemdas) there fore the first step is to add the 1 and the 2 then since there are no exponents you multiply so you multiple 5(3) which is 15 then you can add all the number left to right so 15+2+3= 20 so the answer is 20 hope this helped let me know if you have any questions
At first we must keep in mind that two triangles are similar when they have same angle configuration, that is, each pair of angles is congruent. If ABC and DEF, then and . Hence, and .