How do I do this stats problem?

A recent survey reported that in a sample of 300 students who attended college, 105 work at least 20 hours a week. In a sample of 225 students attending private colleges, only 20 students work at least 20 hours a week. What is the test value

How do I do this stats problem?
phat1 = 105/300 = 0.35


phat2 = 20/225 = 0.089





phat = (105+20)/(300+225) = 0.238





z = (phat1-phat2) divided by


sqrt(phat(1-phat)(1/n1+1/n2))


= (0.35-0.089) divided by


sqrt(0.238(0.762)(1/300+1/225))


= 6.95
Reply:For student attend college, 105 out of n1 = 300 work atleast 20 hours a week, i.e. p1 = 0.35





For student attend college, 20 out of n2 = 225 work atleast 20 hours a week, i.e. p2 = 0.088





For two-proportion z-test,


z = [(p1-p2) - (p2-p1)]/sqrt{[p1(1-p1)/n1]+[p2(1-p2)/n1...


z = 16.3602.