Answer:
She will have 142 watermelons
Explanation:
First let's put our ratio
10 : 71
Since our lemons are now 20 instead of 10 we will divide 20 by 10 to see how many time we multiplied it by.

which equals 2
To find our water melon we will multiply it by 2

which equals 142
She will have 142 watermelons