we have to find the TLB Hit Ratio.
Given EMAT = 120, TLB lookup = 40, Memory = 160 everything in millisec.
Now,
EMAT = t + m + pm here p is (miss ratio)
180 = 40 + 120 +p(120)
120p = 20
so, p = 0.166 (.ie miss ratio) to find hit ratio use hit ratio = 1-p = 1 - 0.16 = 0.844