Idon't know what to do for this one

How much dextrose 70% must be mixed with dextrose 5% to prepare 1,000 ml of dextrose 20%?

It says factor each expression 49x-28?

Which of the expressions (on the photo document i inserted) together represent all solutions to the following equation? 8cos(12x)+4=-4 *the answer should be in degrees.* > i would like for someone to explain the process to find the solutions for this.