How is it no solution? And how can I tell from just looking? PLEASE HELO ASAP!

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

How do you determine if an ordered pair is a solution to a given equation?

The monthly texting plan of all star cell is $11 per month and $0.25 per text. the monthly texting plan of top line cell is $14 per month and $0.15 per text. a student wants to set up a system of equations to find the number of texts for which the total monthly cost of the two companies is the same. he uses the variables x and y. he lets y represent the total monthly cost. what will x represent? x = number of texts x = cost of the total number of texts x = total monthly cost x = cost of each text