Question

Julia wrote 14 letters to friends each month for y months in a row. Write an expression to show how many total letters she wrote.

Answer 1

let y represent number of months in a row and
let S represents sum of letters that have been sent in y number of months

This simply means that we can write equation:
14*y = S

For any number of months we express it in equation above and we get total number of letters she wrote.

Answer 2

Julia wrote 14 letters to friends each month for y months in a row means that Julia wrote 14 letters per month for y months, so the expression will be;
14y. In conclusion, 14y is an expression to show how many total letters she wrote. Have a nice day!