Answer
110 minutes
Work Step by Step
We first find the cost of 24, 90 minute calls. Doing this, we find:
$$ =24\times 90 \times .005 \\ = 10.8$$
Thus, in the Phillipines, with $=20-10.8=9.2 \ dollars $ left on the card, the length of time the calls could be made is:
$$ =\frac{9.2 \ dollars}{.084 \ dollars \ per \ hours} \\ = 110 \ minutes$$
