What is the variable in the expression 2X - 25

Josie buys a pair of boots that retail for $52.00 dollars, however they are currently on sale for 25% off how much does josie pay for the boots if there is also a 6% sales tax on them

Aliter of water contains about 3.35 x 10^25 molecules. a certain river discharges about 2.9x 10^8 l of water every second. about how many molecules does the river discharge every minute? write your answer in scientific notation

Answer this all of it i don’t know how to do it i wasn’t there because i was sick and it’s a nti today so i home not knowing what to do