Ms Writeacher my math work book which is a fifth grader Harcourt Math Practice Workbook does not say what Tues so my mon think it has to be the same Tues in the week of the other days

Here's your question:

"kirk grew a crystal in science class. On monday it was 13/16 inch tall. it had grown 1/4 inch bet friday and monday. It had grown 1/2 inch between Tues and Fri. How tall was Kirk'a crystal on Tues?"

The crystal was 9/16 inch on Friday.
13/16 = 4/16 = 9/16
It grew 2/16 inch each day.

On the previous Tuesday, it must have been 3/16 inch.
9/16 - 6/16 = 3/16

On the following Tuesday (after it was 13/16 inch) it was 15/16 inch.