Write the expression as a single fraction and simplify.

3/a + 3/b

Is this when you cross multiply and get 3a + 3b? Except the answer has to be a fraction so I am not sure.

You did the right thing to get the numerator. Now just put it all over the common denominator:

(3a+3b) / ab

when you're solving equations, the cross-multiplying affects both sides of the equation. When just evaluating an expression, you need to remember why you are cross-multiplying. It's to put everything over the common denominator.

Thank you!!!

To write the expression 3/a + 3/b as a single fraction, you need to find a common denominator for the two fractions. In this case, the common denominator is the product of a and b, which is ab.

To get the fractions with a common denominator of ab, you need to multiply the first fraction 3/a by b/b, and the second fraction 3/b by a/a.

This gives you (3*b)/(a*b) + (3*a)/(a*b).

Now, you can combine the fractions over the common denominator ab:

(3b + 3a)/(ab).

Therefore, the expression 3/a + 3/b as a single fraction is (3b + 3a)/(ab).