The information for two pay as you go cell phone companies is given
on call 3.5 hours : $10
1/2hour: 1.25
what is the unit rate in dollars per hour for each company
can some one me ?

One company wants $10 per 3.5 hours, so they want 10 / 3.5 ≈ 2,86 dollars per hour (after rounding to the closest hundreths).

Second company wants $1.25 per half an hour, so they want 2 * 1,25 = 2,50 dollars per hour.

The unit rate is 2,86:2,50

The answer would be (c)