To find out how much it would cost to purchase 7.5 lbs of walnuts, i can use the given information to set up a proportion:

Cost
Weight
=
Cost of 3/4 lb
Weight of 3/4 lb
Weight
Cost
​
=
Weight of 3/4 lb
Cost of 3/4 lb
​


Given that it costs $3.45 to buy 3/4 lb of chopped walnuts, the cost of 3/4 lb of walnuts is $3.45.

Now, we can plug these values into the proportion:

Cost
7.5
=
3.45
3
4
7.5
Cost
​
=
4
3
​

3.45
​


To solve for the cost of 7.5 lbs of walnuts, we first find the cost of 1 lb:

Cost
1
=
3.45
3
4
1
Cost
​
=
4
3
​

3.45
​


To divide by a fraction, we multiply by its reciprocal:

Cost
=
3.45
×
4
3
Cost=3.45×
3
4
​


=
4.6
=4.6

So, the cost of 1 lb of walnuts is $4.6.

Now, to find the cost of 7.5 lbs of walnuts, we multiply the cost of 1 lb by 7.5:

7.5
×
4.6
=
34.5
7.5×4.6=34.5

So, it would cost $34.5 to purchase 7.5 lbs of walnuts.