The equation of this line is...?

What is the simplified form of (3.25x10^3)(7.8x10^6) written in scientific notation?

Gabriel determined that his total cost would be represented by 2.5x + 2y – 2. his sister states that the expression should be x + x + 0.5x + y + y – 2. who is correct? explain.

In a column proof the right column states your reasons