18y + –20y − –5y + –1 = –4

The complete question in the attached figurewe have that3^y = 8we can apply base 3 logarithm to both sides.  base 3 log (3^y) = base 3 log (8)y * [base 3 log 3] = base 3 log (8)we know thatbase 3 log 3 = 1therefore  y = base 3 log (8)the answer is  y = base 3 log (8)