let for machine m1 time be t and for machine m2 time be 6t
for m1 time of alu instructions= x1 and other instructions be y1
for m2 time of alu instructions= x2 and other instructions be y2
so , for m1: t=x1+y1, where x1=0.6t // as given alu of m1 takes 60% of total execution time, so y1=0.4t
as given in question time taken by other instruction in both machine is equal so y2=y1=0.4t
and x2+y2=6t , so x2=5.6t
% time taken by alu=(5.6/6*100)%
=93%

let for machine m1 time be t and for machine m2 time be 6t

for m1 time of alu instructions= x1 and other instructions be y1

for m2 time of alu instructions= x2 and other instructions be y2

so , for m1: t=x1+y1, where x1=0.6t // as given alu of m1 takes 60% of total execution time, so y1=0.4t

as given in question time taken by other instruction in both machine is equal so y2=y1=0.4t

and x2+y2=6t , so x2=5.6t

% time taken by alu=(5.6/6*100)%

=93%