Step 1:

Let $X$ be the random variable denoting the number of times heads turns up when 4 coins are tossed simultaneously.

The probability of getting a head in 1 throw =$\large\frac{1}{2}$$=p$

$X\sim B(4,\large\frac{1}{2})$

Step 2:

The probability distribution of $X$ is given by

$P(X=x)=nC_xp^xq^{n-x}$

$P(X=x)=4C_x(\large\frac{1}{2})^x(\large\frac{1}{2})^{4-x}$

$\qquad\qquad=(\large\frac{1}{2})^4$$4C_x\qquad x=0,1,2,3,4$

Step 3:

$P(X\leq 2)=P(X=1)+P(X=2)$

$\qquad\qquad=(\large\frac{1}{2})^4$$[4C_0+4C_1+4C_2]$

$\qquad\qquad=(\large\frac{1}{2})^4$$[1+4+6]$

$\qquad\qquad=\large\frac{11}{16}$