Jenny wants to multiply out the brackets in the expression 3 (2a+1)

she writes 3 (2a+1) = 6a+1

show why jenny is wrong

The correct answer should be 6a + 3.

She is wrong, because she forgot to distribute the 3 to the one. When multiply numbers into a binomial, you need to multiply both terms by that number.

3 (2a+1) = 6a + 3

it's 3 instead of 1