Choose the equation with the lowest answer

10 - 0.01
10 × 0.01
10 ÷ 0.01
10 + 0.01

If f(x)=3x+1 and f^-1=x-1/3, then f^-1(7)=

Given abcd ac=38 and ae=3x+4 find the value of x

Each person in an it department of 25 people works on at least one of 3 major projects: system security, program implementation, platform development. 10 people work on system security, 13 work on program implementation, and 12 work on platform development. 4 people work on system security and platform development, 5 people work on program implementation and platform development, and 2 people work on all three projects. how many people work on system security and program implementation?