Find the sum of the first 8 terms of the series 3 + 6 + 9 + …, given that a8 = 24.

Step-by-step explanation:

You want to use the sum of an arithmetic sequence formula.

(a1 + an) × n/2

a1 is the first term and an is the last term. n is the number of terms.

In this case: (3+24) × 8/2 = 27×8/2 = 27×4 = 108

answer: 25 is the correct answer

step-by-step explanation:

x = -3

y = -18

step-by-step explanation:

to solve by substitution, substitute one variable and solve for the other. then substitute again to find the remaining variable.

x-1/3(3x-9) = -3 since y=3x-9 substittute y.

x-1/3(3x-9)=-3

x + x +3 = -3

2x+3=-3

2x+3-3= -3-3

2x=-6

x=-3

substitute again into y=3x-9

y=3(-3)-9

y=-9-9

y=-18