I need help with questions 3 and 4 The one in black is an example the teacher gave me but I still don’t understand (btw sorry for the bad writing)

Consider circle h with a 3 centimeter radius. if the length of minor arc what is the measure of zrst?

Alicia puts $400 in a bank account. each year the account earns 5% simple interest. how much money will be in her bank account in six months?

John used linear combination to solve the system of equations shown. he did so by multiplying the first equation by -3 and the second equation by another number to eliminate the x-terms. what number did jonas multiply the second equation by? 4x-6y=23x+5y=11