One approach to this type of word problem is to list the information you are given:

Step 1:

$19.95 = basic monthly charge

$0.05 = per minute charge$23.74 = total monthly billx = the number of minutes used

Step 2:

Next, put these things into an algebraic expression.

Total monthly bill = basic monthly charge + (per minute charge) * (number of minutes used)

Step 3:

Now, plug in the numbers for your first step and solve.

$23.74 = $19.95 + $0.05x

-19.95 -19.95

$3.79 = $0.05x

divide each side by 0.05 to find x

You could also rewrite the problem at step 2. It just depends if you like working with numbers (algebra, variables, etc.) or thinking about the problem in words (more a verbal style of learning).

Number of minutes used = cost for minutes / per minute charge

Number of minutes used = (Total monthly charge - basic monthly charge) / per minute charge