Answer:
90 cubic inches
Step-by-step explanation:
-2x + xy = 30.....when y = 8
-2x + 8x = 30
6x = 30
x = 30/6
x = 5 <==
The desired number is the difference between the number of messages sent by the 16th day and the number sent by the 9th day:
... n = t(16) - t(9)
... n = (40×√16) - (40×√9)
... n = 40×(4 - 3) = 40
40 text messages were sent between the ninth and sixteenth day of the month.
Answer:

Step-by-step explanation:

Hope this helps ;) ❤❤❤