SOLUTION
The formula for growth rate is given below;
[tex]y=a(1+r)^x[/tex]Where;
y = number of infections,
a = initial number of infections (20),
r = rate (30% or 0.3) and
x = the week to find (10)
[tex]\begin{gathered} y=a(1+r)^x \\ y=20(1+0.3)^{10} \\ y\text{ = 20 (13.7858)} \\ y\text{ = 275.72} \end{gathered}[/tex]The number of infections in week 10 will be 276.