We bought a total of 90 books at the store. Math books cost $4 and history books cost $5. The total price was $397. How many math books did we buy?	Select the correct option.
A) 47
B) 53
C) 56
D) 61
E) 64
Let M be the number of math books and let H be the number of history books.   M+H=90.   H=90-M.   4M+5H=397.   4M+5(90-M)=397.   -M+450=397.   M=450-397= 
<gadget id="calculator">450-397</gadget>
<output>53</output>
53.   The answer is 53.
<result>B</result>
We bought a total of 90 books at the store. Math books cost $4 and history books cost $5. The total price was $397. How many math books did we buy?