Zaira is getting 2 questions wrong per every seven. In total 245 questions how many is she getting wrong?

The size of a certain cell is 2.5*10^-9m. another cell is 1.5*10^3 times larger. how large is the larger cell in scientific notation?

In a class, there are 12 girls. if the ratio of boys to girls is 5: 4 how many boys are there in the class

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?