To find angle $ \beta $ use formula:
$$ \alpha + \beta = 90^o $$After substituting $ \alpha = 150^o $ we have:
$$ 150^o + \beta = 90^o $$ $$ \beta = 90^o - 150^o $$ $$ \beta = -60^o $$The result has to be greater than zero. $ \Longrightarrow $ The problem has no solution.