Answer:111Step-by-step explanation:a1 = -12a27 = 66Now using the formula an = a1+(n-1)d we will find the value of dhere n = 27a1 = -12a27 = 66Now substitute the values in the formula:a27 = -12+(27-1)d66= -12+(26)d66 = -12+26 * d66+12 = 26d78 = 26dnow divide both the sides by 2678/26= 26d/263 = dNow put all the values in the formula to find the 42 terman = a1+(n-1)da42 = -12 +(42-1)*3a42 = -12+41 *3a42 = -12+123a42 = 111Therefore 42 term is 111....