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Work Shown:
a = first term
a*(2/3) = (2/3)a= second term
(2/3)a*(2/3) = (4/9)a = third term
note how I multiplied each previous term by the common ratio (2/3) to get the next term
Add up the three terms
a + (2/3)a + (4/9)a = (9/9)a + (6/9)a + (4/9)a = (19/9)a
Set this equal to 171, which is what we want the first three terms to sum to, then solve for 'a'
(19/9)a = 171
a = (9/19)*171
a = 81 is the first term
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Checking the answer:
a = 81 = first term
(2/3)*a = (2/3)*81 = 54 = second term
(4/9)*a = (4/9)*81 = 36 = third term
adding up the three terms gets us
81+54+36 = 171
so we have confirmed the answer
