Question

you practice the piano for 30 min. each day. Write and solve an equation to find the total time t you spend practicing the piano in a week.

Answer 1

Lets get all the information we need first.
A week has 7 days, you practice 30 min each day, so in a week you will practice a total time t of 30 min for 7 times, that is:
t = 7day(30 min/day)
t = 210 min
So in a week you will practice a total of 210 minutes.

Answer 2

There are 7 days a week, and you spend 30 minutes each day practicing
T = Time spend studying
30 * 7 = T

T = 210 minutes studying!