Answer & Explanation:
So the alien is 90 cm at birth. Your just going to add 23 for each year to the birth number of 90, because a year = 23 cm of growth
At 2 years it will be
90 + 23 + 23 = 136
At 4 years it will be
90 + 23 + 23 + 23 + 23 = 182
At 6 years it will be
23 x 6 = 138, 138 + 90 = 228
At 7 years it will be
23 x 7 = 161, 161 + 90 = 251