Add (1.3t3 + 0.4t2 – 24t) + (8 – 18t + 0.6t2) for each term in the second polynomial, enter the letter showing where that term should be placed to add the polynomials vertically. 1.3t3 + 0.4t2 + (–24t) =0.6t^2 =0t^3 =8 =-18t

(1.3t3 + 0.4t2 – 24t) + (8 – 18t + 0.6t2) 

In adding polynomials, make sure that each term is grouped together. 

1.3t³ + 0.4t² - 24t
         + 0.6t² - 18t  + 8
1.3t³ + 1.0t² - 42t + 8

In a polynomial equation, arrangement of each term is dependent on the exponential number. It should be from the highest exponent to the lowest. 

None of the options you showed are it.