Find the ordered pair $(s, t)$ that satisfieFor a certain value of $k,$ the system \begin{align*} 3a + 4b &= 7,\\ 6a + 4b &= k- 4b \end{align*}has infinitely many solutions $(a, b).$ What is $k$?S the system \begin{align*} \dfrac{s}{2} + 5t &= 3,\\ 3t - 6s &= 9. \end{align*}

The weekly amount spent by a company for travel has an approximately normal distribution with mean = $550 and standard deviation = $40. a) what is the probability that the actual weekly expense will exceed $570 for more than 20 weeks during the next year? (note: one year = 52 weeks) b) what is the probability that actual weekly expenses exceed $580 for 10 or more, but 16 or fewer weeks during the next year?