We used sampling technique to collect samples throughout the instance of Options a and b because here each successive sample frame has the same gap of 10 (in the example) and in 'b' is 1, but we use a simple random sampling in 'b' and 'c' to collect the test because they can't follow any specific pattern from of the collecting systems here.
Combine like terms: y=5x+4 and y=4x+1. Sub one in: 4x+1=5x+4. -1x=3. X=-3. Sub into other one: y=4•-3+1. Y=-12+1. Y=-11. Check it: -11=5•-3+4. -11=-15+4. -11=-11. So X=-3 and Y=-11 :)
In this question you have to use BODMAS. This indicates that you have to do the equation in the brackets first. Therefore, 3x15= 45. Then you add 25, which will give you 70.
