The question i need on is 15.5z= -77.5 . i really don't get it : )

The function a represents the cost of manufacturing product a, in hundreds of dollars, and the function b represents the cost of manufacturing product b, in hundreds of dollars. a(t) = 5t + 2 b(t) = 7t - 2t +4 find the expression that describes the total cost of manufacturing both products, a(t) + b(t). a. 7t^2 - 7t + 2 b. 7t^2 + 3 +6 c. 7t^2 + 7t - 6 d. 7t^2 - 3t + 6

1. suppose that scores on a knowledge test are normally distributed with a mean of 71 and a standard deviation of 6. a. label the curve: show the mean and the value at each standard deviation: b. if angelica scored a 76 on the test, what is her z-score? (draw her score on the curve above and label) c. what percent of students did angelica score higher than? how can you tell? d. if 185 students took the test, how many students scored higher than angelica?

Write 24/20 in lowest terms. a) 12/5 b) 5/4 c) 6/4 d) 6/5