Question 831708
You have a formula to find any term in a arithmetic sequence and it is
Term = a + d(n - 1) 
in which a is the first term and d is the difference between the terms, and n is the number of the term
ok so we have 11th term is 57, the equation will be
57 = a + d(11-1)
a + 10d = 57
That's the first equation
Now we move to the second one
We have First term is just "a"
and fourth term is a+d(4-1) = a + 3d
We have the sum of first and fourth terms is 29, that means a + a + 3d = 29
2a + 3d = 29 
That's the second equation, now we have a system of 2 equations to solve for a, d
*[invoke linear_substitution "a", "d", 1, 10, 57, 2, 3, 29 ]
Now you know that a = 7, meaning that the first term is 7 
d is 5, so the second term is 12, and the third term is 17
So the answer is 7, 12, 17
TA-DAH
:D