Answer:
30kg
Step-by-step explanation:
what we know is that 3a - 20kg is b. and if a + 3a -20kg = 100kg, it becomes algebra .
So, we move it over to the sides:
4a = 120kg
(here i moved -20kg to the 100kg and did the reverse. I also added the a's)
which means a = 120kg divided by 4
a = 30kg
