Probability is define as:
[tex]P(A)=\frac{Number\text{ of favorable outcome }}{Total\text{ number of outcome}}[/tex]If coin tosses two times then favorable outcome that mean heads chance is =2
total outcome is =4
so probability is:
[tex]\begin{gathered} P(A)=\frac{2}{4} \\ =\frac{1}{2} \end{gathered}[/tex]