El cuadro de un numero natural menos nueve es igual a 315. ¿ cual es ese numero ?

Two lines parallel to the same plane are parallel to eachother

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?

On the first of each month sasha runs a 5k race she keeps track of her times to track her progress her time in minutes is recorded in the table