lets denote

with '1' if the coin is heads

with '0' if the coin is tails

the result two heads and two tails can be written as 1100

we need to count the different 4-digit numbers formed from 1,1,0 and 0:

1,1,0,0

1,0,1,0

1,0,0,1

0,1,0,1

0,0,1,0

0,1,1,0

there 6 different 4-digit numbers formed by 1,1,0 and 0

the total number of 4-digit numbers formed by 1s and 0s only is 2*2*2*2 = 16

the probability = 6/16 = 0.375 or 37.%