Plzz i wanna solution within a minute​

Afruit stand has to decide what to charge for their produce. they need $10 for 4 apples and 4 oranges. they also need $15 for 6 apples and 6 oranges. we put this information into a system of linear equations. can we find a unique price for an apple and an orange?

Twice the sum of a number and 4 is equal to three times the difference of the number and 7. find the number.

What is the number 321,000,000 in scientific notation? also what is the number? ?