The arithmetic sequence is .

Find the common difference by subtracting successive terms.

The common difference is –4.

Subtract 4 to last term of the sequence to get the next termin the sequence.

Continue subtracting 4 untill the next three terms are found.

–78 – 4 = –82, –82 – 4 = –86 and –86 – 4 = –90.

The next three terms are –82, –86, –90.