The general equation for an aritmetic sequence is t(n) = mn + b.
Use t(8) = 1056 to write an equation.
t(8) = m(8) + b or 1056 = 8m + b
Use t(13) = 116 to write another equation.
Solve the system of equations you wrote for m and b.
t(n) = −188n + 2560
To find t(5), substitute 5 for n in the equation that you wrote.