Qué características tiene un rombo

Leslie started last week with $1200 in her checking account. during the week, she wrote the checks below.

Cd is the perpendicular bisector of both xy and st, and cy=20. find xy.

Julie begins counting backwards from 1000 by 2’s and at the same time tony begins counting forward from 100 by 3’s.   if they count at the same rate, what number will they say at the same time?