Which line on the graph below has a slope of zero?

On a coordinate plane, line Q is horizontal, line P has a positive slope, line R is vertical, and line S has a negative slope.
P
Q
R
S

The boiling point of water at an elevation of 0 feet is 212 degrees fahrenheit (°f). for every 1,000 feet of increase in elevation, the boiling point of water decreases by about 2°f. which of the following represents this relationship if b is the boiling point of water at an elevation of e thousand feet? a) e = 2b - 212 b) b = 2e - 212 c) e = -2b + 212 d) b = -2e + 212

22. catie is starting a babysitting business. she spent $26 to make signs to advertise. she charges an initial fee of $5 and then $3 for each hour of service. write and solve an inequality to find the number of hours she will have to babysit to make a profit. interpret the solution.!

Cos^2x+cos^2(120°+x)+cos^2(120°-x)i need this asap. pls me