How do you solve this one 10x^2-25=x^2

What is the best way to answer questions with a x expression in the question. for example 3x + 10x=?

You buy five cds at a sale for $5.95 each. write an expression for the total cost of the cds.then use the distributive property and mental math to evaluate the expression.

Ur environment is very sensitive to the amount of ozone in the upper atmosphere. the level of ozone normally found is 4.04.0 parts/million (ppm). a researcher believes that the current ozone level is not at a normal level. the mean of 2525 samples is 4.44.4 ppm with a standard deviation of 0.80.8. assume the population is normally distributed. a level of significance of 0.020.02 will be used. make the decision to reject or fail to reject the null hypothesis. answer tables