Find the missing length. The triangles are similar.

Can someone help me?

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?

When solving a logarithm equation, how do you find the missing variable ?

Which expression gives the distance between the two points 2 5 and 4 8