Amanda is making some strawberry preserves. she has three sizes of canning jars. small pint size, medium quart size, and large half gallon size. in all she has 22 jars. she has three time as many small jars as large and three fewer mediums than large. how many small jars does amanda have?
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The answer is 15.

S - small jar
M - medium jar
L - large jar

In all Amanda has 22 jars: S + M + L = 22
She has three time as many small jars as large: S = 3L
She has three fewer mediums than large: M = L -3

Now, we can use the method of substitution:
S = 3L       
M = L - 3

 S  +   M  + L = 22
3L + L - 3 + L = 22
3L + L + L = 22 + 3
5L = 25
L = 25 ÷ 5 = 5

Since S = 3L, then:
S = 3 · 5 = 15

Amanda has 15 small jars.