I am working on cross products of proportions. one question is 5/7 = 3w/21

Can someone help?

21 w = 105 is the next step if you match the "cross products" of numerator-denominator pairs.

Then divide each side by 21 to get w.

multiply both sides of this equation by 21

(5/7) 21 = (3w/21) 21
5*3 = 3 w
now divide both sides by 3
5 = w

(I do not like the cross multiplication language. It is safer to multiply both sides by a common multiple of the denominators, which is really what cross multiplication means.)
If you did it with cross multipication you would have
5 * 21 = 7 * 3 * w
5 * 21 = 21 * w
5 = w

Certainly! I can help you solve the proportion equation 5/7 = 3w/21. To solve proportions like this, we can use cross products.

The cross product of the proportion is found by multiplying the numerator of the first fraction with the denominator of the second fraction, and vice versa. In this case, the cross products would be (5 * 21) and (7 * 3w).

Now, let's solve the equation step by step:

1. Cross product: (5 * 21) = (7 * 3w)
Simplifying, we get: 105 = 21w

2. Divide both sides of the equation by 21:
105/21 = 21w/21
Simplifying, we get: 5 = w

Therefore, the value of w that satisfies the proportion equation 5/7 = 3w/21 is w = 5.