26 . C
It helps to draw a Venn diagram of the problem situation:As shown in the diagram, add up the number of members who either do
all three activities or any two of the activities: 8 + 10 + 5 + 15 = 38. The
remaining members use only one of the services, so 50 − 38 = 12
members.27 . C
To solve the equation for x, first multiply both sides by (x − a^2 ) to get y(x −
a^2 ) = x + 7 a. Use the distributive property on the left-hand side: yx − ya^2 =
x + 7a. Add ya^2 and subtract x from both sides of the equation to get yx −
x = ya^2 + 7 a. Factor out the x from the left-hand side: x(y − 1) = ya^2 + 7 a.
Finally, divide both sides by (y − 1) to solve for x in terms of y and
28 . A
First, raise both sides of the equation to the third power to eliminate the
cube root on the left-hand side. This results in or