Izzie recently took a math test where each correct answer (a) on the main part of the test was worth 6.4 points. She also correctly solved a bonus question worth 11 points. Using the equation 6.4a + 11 = 81.4, how many correct answers (a) did Izzie have on the main part of the test?
6.4a + 11 = 81.4
6.4 a = 70.4
a = 70.4 / 6.4 = 11