X2 can be combined with X?

Not sure if you mean multiplying or adding by "combine". But generally the rule of thumb with exponents is when you are adding and they are not like terms, you cannot combine the two terms together. So in other words, they would be left as x²+x. However, when you are multiplying you can add the exponents together. So, it will be like this: x²·x = x³

step-by-step explanation:

ok so im not 100% sure but you would start by adding 5.1t and 1.9t beacuse they have the same variable. that is 7t.   then add -3.6 + 1.2 which is -2.4

so then keep that as -2.4 + 7t. i apologize if this is incorrect. best luck on your test < 3

step-by-step explanation: