Place value: tens and ones

A two-digit number is built from tens and ones. In 35 the left digit counts tens and the right digit counts ones, so 35 is 3 tens (30) and 5 ones. When you hear 'thirty-five', the 'thirty' already fills the tens column, so the 5 sits in the ones column beside it — you do not write 30 and 5 next to each other. Say the tens digit first and write it on the left, then the ones digit on the right.