Answer:
10:7
Explanation:
ratios are simply just like fractions!
this ratio (40:28) can be re-written as 40/28
now, you can simplify this to its lowest terms
40/28=20/14=10/7
first in those steps i re wrote the question, then divided by two, then divided by two again !
so, 40:28=10:7
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you can even check this by cross multiplying, since ratios are fractions

40x7=28x10
280=280
they are equivalent which means our ratio is correct :)
hope this helped <333