How many 2-digit numbers have the digit 7 only once?

17, 27, 37, 47, 57, 67, 87, 97, so 8 of them

Step-by-step explanation:

those are all the 2 digit numbers with only one seven in them

hope this answers your question

d. millimeters per hour.

step-by-step explanation:

we are given that,

carlo used a rain gauge to measure the amount of water his lawn is receiving from the sprinklers.

since, according to the options, we see that,

water cannot be measured by 'miles per hour', 'meters per second' and 'grams per seconds'.

we get that, the water can be measured by 'millimeters per hour'.

hence, the appropriate rate for describing the amount of water is 'millimeters per hour'.