ANSWERS
(a) 7.61 USD
(b) 1247.98 MXN
EXPLANATION
We know that on March 8, 2017, 1 USD was worth 19.61 MXN.
(a) To find how many dollars was 149.23 MXN worth on that date, we have to divide this amount by 19.61,
[tex]149.23\text{ }MXN\cdot\frac{1\text{ }USD}{19.61\text{ }MXN}\approx7.61[/tex]Hence, 149.23 Mexican pesos were worth 7.61 US dollars.
(b) Now, to find how many Mexican pesos were 63.64 USD worth on that date, we have to multiply it by 19.61 instead,
[tex]63.64\text{ }USD\cdot\frac{19.61\text{ }MXN}{1\text{ }USD}\approx1247.98\text{ }MXN[/tex]Hence, 63.64 US dollars were worth 1247.98 Mexican pesos.