Answer:
[tex]B = 325[/tex]
Step-by-step explanation:
Given
Total = 900
Singing = 600
Dancing = 500
None = 125
Required
Determine the number of students that participate in both
Representing; Singing with S, Dancing with D, Both singing and dancing with B and None with N;
In Set Notation;
[tex]Total = (S - B) + (D - B) + N + B[/tex]
Substitute 900 for Total, 600 for S, 500 for D and 125 for N
[tex]900 = (600 - B) + (500 - B) + 125[/tex]
Open Brackets
[tex]900 = 600 - B + 500 - B + 125 + B[/tex]
Collect Like Terms
[tex]900 = 600 + 500 + 125 - B - B + B[/tex]
[tex]900 = 1225- B - B + B[/tex]
[tex]900 = 1225- B[/tex]
Collect Like Terms
[tex]900 - 1225 = -B[/tex]
[tex]-325 = -B[/tex]
Multiply both sides by -1
[tex]-1 * -325 = -B * -1[/tex]
[tex]325 = B[/tex]
Reorder
[tex]B = 325[/tex]
Hence, the number of students that do not participate in both is 325