Together, that is 40 percent of the total sample. You can subtract that 40 percent from 100 percent and determine 60 percent of the sample must be adenine and thymine together. Since those two bases always exist in equal concentrations, you know the DNA sample is 30 percent adenine.
This is the case since earthquakes form directly from tectonic plates. It happens when 2 tectonic plates pass by each other and causes fiction from the bumby sides of the plates
