1.) Diego paid $47 for 3 tickets to a concert. Andre paid $141 for 9 tickets to a concert. Did they pay at the same rate (what was the value they paid for 1 ticket)? How do you
know?

They pay at the same rate.
The value they paid for one ticket is 15.67$
How do you know:
Andre paid for 3 times more tickets than Diego. 47 x 3 is 141, so they are at the same rate.
47 / 3 is 15.667, which rounds up to 15.67$ in money terms.