Subtract 0.456-0.69=0.234 why​

Atemperature of 1.64◦f corresponds to answer in units of ◦c.

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?

The value of the expression 16-^3/4 8 1/8 -6 6 1/40 1/64