For non pipeline:50ns*100=5000ns(as for each task it takes 50ns, therefore for 100task it is 5000ns)
For pipeline system:
#stages (k) =6
1task time taken=10ns
Therefore for 100 task,
We use the formula
{1*k+(n-1)*1}*clock cycle
{1*6+(100-1)*1}*clock cycle =105*10 bs=1050ns
That means ,the first instruction will take 6 stages but rest of the instructions will take 1 cycle.
For speedup,
Time without pipeline/time with pipeline=5000/1050=4.76.