Let S = {(-1,0,1), (2,1,4)}. The value of k for which the vector (3k+2,3,10) belongs to the linear span of S is

One cell phone plan charges $20 per month plus $0.15 per minute used. a second cell phone plan charges $35 per month plus $0.10 per minute used. write and solve an equation to find the number of minutes you must talk to have the same cost for both calling plans.