Need some help in math ​

Two customers went to a post office. first customer paid $12 for 14 and 5 envelopes the second paid 24.80 for 10 postcards and 15 envelopes. what is cost of each envelope?

The description below represents function a and the table represents function b: function a the function is 5 more than 3 times x. function b x y −1 2 0 5 1 8 which statement is correct about the slope and y-intercept of the two functions? (1 point) their slopes are equal but y-intercepts are not equal. their slopes are not equal but y-intercepts are equal. both slopes and y intercepts are equal. neither slopes nor y-intercepts are equal.

Find the volume of the solid obtained by rotating the region enclosed by the curves y=1x and y=7^-x about the x-axis. (use symbolic notation and fractions where needed.) volume =