We first define variables for the numbers of female and male students last semester
\(F_1 = \text{number of female students last semester}\)
\(M_1 = \text{number of male students last semester}\)
We translate the total number of students last semester
\(F_1 + M_1 = 17,600\)
We translate the 10 percent increase in female students
\(F_2 = 1.1 \times F_1\)
We translate the 22 percent increase in male students
\(M_2 = 1.22 \times M_1\)
We translate the condition that the difference remains the same
\(F_1 - M_1 = F_2 - M_2\)
We substitute for \(F_2\) and \(M_2\) and simplify
\(F_1 - M_1 = 1.1F_1 - 1.22M_1\)
\(-0.1F_1 + 0.22M_1 = 0\)
\(0.22M_1 = 0.1F_1\)
We isolate \(F_1\) in terms of \(M_1\)
\(F_1 = 2.2\times M_1\)
We substitute into the total to form one equation in \(M_1\)
\(2.2M_1 + M_1 = 17,600\)
\(3.2M_1 = 17,600\)
We divide to solve for \(M_1\)
\(M_1 = \frac{17,600}{3.2} = \frac{176,000}{32} = \frac{160,000}{32} + \frac{16,000}{32} = 5,000 + 500 = 5,500\)
We find the number of female students last semester
\(F_1 = 2.2 \times 5,500 = (2 + 0.2) \times 5,500 = 11,000 + 1,100 = 12,100\)
We calculate the new number of female students
\(F_2 = 1.1 \times 12,100 = 12,100 + 1,210 = 13,310\)
We calculate the new number of male students
\(M_2 = 1.22 \times 5,500 = 5,500 + 1,210 = 6,710\)
We sum to find the total this semester
\(\text{Total} = F_2 + M_2 = 13,310 + 6,710 = 20,020\)
Answer D
Hope this helps!
ʕ•ᴥ•ʔ