Lisa and Tim make necklaces. Lisa uses 5 red beads for every 3 yellow beads. Tim uses 9 red beads for every 6 yellow beads. is the ratio of red beads to yellow beads in Lisa's necklace equivalent to the ratio in Tim's necklace?

No. The ratio of red beads to yellow beads in Lisa's necklace is not equivalent to the ratio in Tim's necklace

Proportionality of two ratios is check using either fraction or colon.

where:

a/b = c/d or a:b = c:d

5/3 = 9/6 or 5:3 = 9:6

When two ratios are equal, then the cross products of the ratios are equal.

a x d = 5 x 6 = 30

b x c = 3 x 9 = 27

In this case, cross products of the ratios are not equal, thus, the two ratios are not equal.

For the ratios to become equal,

Tim's necklace must have 10 red beads for every yellow beads.