Let
f ------> the amount of money Lisa will have saved
d -----> number of times that she walking the neighbor's dog
so
Remember that
The linear equation in slope intercet form is equal to
f=md+b
where
m is the unit rate or slope
b is the y-intercept or initial value
in this problem we have
m=6
b=50
therefore
substitute
f=6d+50
answer is last one option