Set up the original ratio: 3:4 (a.k.a. 3/4 or 3 to 4)
Because 16 correlates to red paint and 3 correlates to red paint the will be in the same location (as the numerator or denominator).
Also, the amount of blue paint is unknown so that is <u>x</u>. <u>4</u> also represents blue paint, so <u>4</u> and <u>x</u> will also be on the same level (as the numerator of denominator).
Well if she added three blue and four red originally, and is now using 16 red then we would divide 16 by the original four. Which means to get the number of blue we are gonna end up multiplying by four. So three times four is twelve. Which means she would use 12 blue and 16 red to get the same color she got with 3 blue and 4 red earlier. The equation, lets use x for blue and y for red, would be 4(3x + 4y) = desired color