I really dont understand this!

The first five terms of a linear sequence are given below. 7 , 12 , 17, 22 , 27 , what is the next term of the sequence?

Achemist has 200 ml of a 10% sucrose solution. she adds x ml of a 40% sucrose solution. the percent concentration, y, of the final mixture is given by the rational function: the chemist needs the concentration of the final mixture to be 30%. how many milliliters of the 40% solution should she add to the 10% solution to get this concentration?

Aline that intersects one of two parallel lines intersects the other also always sometimes never