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Answer:
x = 10
Step-by-step explanation:
Using your number sense, you recognize that a fraction equivalent to 2/5 that has 4 in the numerator is 4/10. This tells you x = 10.
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The usual instructions for solving this algebraically are to "cross multiply", then divide by the coefficient of x.
2/5 = 4/x . . . . given
2x = 20 . . . . . multiply by 5x on both sides
x = 10 . . . . . . . divide by 2
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You can do the above two steps both at once: multiply by 5/2x.
(2/5)(5/2x) = (4/x)(5/2x)
x = 20/2 = 10
