Explanation

given $n(U) = 40$

$n(M) = 55$ % $of$ $40 = 22$

$n(P) = 25$ % $of$ $40$ $= 10$

$n(P∩M) = 25$% $of 40 = 8$

remember 8 is the intersection

thus:

for $n(M) 22 - 8 = 14$

for $n(P)$ $10 - 8 = 2$

so $14 + 8 + 2 + x = 40$

$24 + x = 40$

$x = 40 - 24 = 16$

given $n(U) = 40$

$n(M) = 55$ % $of$ $40 = 22$

$n(P) = 25$ % $of$ $40$ $= 10$

$n(P∩M) = 25$% $of 40 = 8$

remember 8 is the intersection

thus:

for $n(M) 22 - 8 = 14$

for $n(P)$ $10 - 8 = 2$

so $14 + 8 + 2 + x = 40$

$24 + x = 40$

$x = 40 - 24 = 16$