Hate to ask two questions in a day but my book was horrible at explaining how to solve these, question is in picture

Find the value of p for which the polynomial 3x^3 -x^2 + px +1 is exactly divisible by x-1, hence factorise the polynomial

For what values of the variable x is the expression square root of 7x+14+ square root of 7-x a real number?

The party planning committee has to determine the number of tables needed for an upcoming event. if a square table can fit 8 people and a round table can fit 6 people, the equation 150 = 8x + 6y represents the number of each type of table needed for 150 people.