Subtracting like fractions ! tell answer

Need solving this second acceleration problem.

The? half-life of a radioactive substance is 20 years. if you start with some amount of this? substance, what fraction will remain in 120 ? years

Given: p: 2x = 16 q: 3x – 4= 20 which is the converse of p - q? if 2x + 16, then 3x - 4 20. if 3x –4 +20, then 2x # 16. lf 2x = 16, then 3x - 4 = 20. lf 3x – 4= 20, then 2x = 16. o o