cross product property
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Using the cross product property on this proportion gives us the following equation:
20 (2x - 9) = 10 (9)
Use the distributive property and multiply
40x - 180 = 90
Add 180 to both sides
40x = 270
Divide 40 from both sides
x = 270/40
Simplify fraction
x = 27/4
This should be your answer. Let me know if you need any clarifications, thanks!