If you have a mean of 2 and you want to get standard deviation with probability of 90% that the new mean will lie between 1.5 and 2.5. I tried to solve out this question by considering the inverse of Z score

Probability of 90% correspond to z =1.281 then I don't know how to solve out the following equation to get t0 (standard deviation)

Could you help me to solve this equation