System equations

Question

town a and town B were located close to each other and recently merged into one City Town a had a population of 12% African Americans town be at a population of 10% African Americans after demerge the new city has a total of 4000 residents with 10.7% African Americans how many residents did town a and town B used to have town a used to have ____ residence in town be used to have _____ residents

Answer 1

.12x + (4000-x)(.10) = (.107)4000

.12x -.10x = 428-400 = 28

.02x = 28

x = 28/.02 = 1400 in town A

4000-1400 = 2600 in town B