Question 1036053
Call their numbers, p and d.  Then we can write
p + d = 40 and the value equation is
p + 10d = 211 (we work in cents)
Now subtract equations and get
p + d = 40
-(p + 10d = 211)
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-9d = -171
d = 19 dimes and that means she has
p = 21 pennies