in these problems u substitute the number specified so in this problem you would put 6 in for k which would makes the problem 5* 6-10c+8 then you put 2 in for c which makes the problem 5*6-10 *(times) 2+8 so then u do the order of operation so 5 times 6 and u get 30 so now the problem is 30 - 10 *2+8 so now you do 10 times 2 is 20 so the problem is 30-20+8 now you do it from left to right so 30 -20 wich is 10 so the problem is 10 +8 and 10 plus 8 is 18 so i would say that it is
18
hope i help
