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 Proportions Proportion An equation in which two ratios are equal is called a proportion. Two ratios and are a proportion when Remember the two ratios are equals if their cross products are equal a·d = b·c You can also use the cross product to find a missing number: Solve: $\frac{-5}{2}=\frac{t}{-8}$$\fs2(-5)(-8)=2t\;\Rightarrow\;\;40=2t\;\Rightarrow\;2t=40\;\Rightarrow\;\;t=20$ Find x to get a proportion $\frac{10}{12}=\frac{x}{6}$. Find x to get a proportion: $\frac{4}{40}=\frac{x}{180}$ Solution x=