[tex]first \: positive \: charge = q1 = 20[/tex]
[tex]1micro \: = {1}^{ - 6} [/tex]
[tex]1q = 20 \times 10 {}^{ - 6} [/tex]
[tex]second \: charge = q2 = 100 \times 10 {}^{ - 6} [/tex]
[tex]formula = f = \frac{k \times q1 × q2}{d {}^{2} } [/tex]
remember
[tex]k = 9 \times {10}^{9} [/tex]
change distance 150cm to 1.5m
putting values
f =[tex] \frac{9 \times 10 {}^{9} \times 20 \times 10 {}^{ - 6} \times 100 \times {10}^{ - 6} }{1.5 {}^{2} } [/tex]