How did Kublai Khan’s empire differ from the Mongol Empire built by Genghis Khan?

Khan’s empire did not expand past ancient China.
Khan’s empire did not conquer China’s capital.
Khan’s empire did not conquer southern China.
Khan’s empire did not unify the Chinese provinces.

If x + 10 = 70, what is x? a. 40 b. 50 c. 60 d. 70 e. 80

Ascientist wants to use a model to present the results of his detailed scientific investigation. why would a model be useful? a )because the model makes the concepts easier to understand b) because the model is easy to put together and to use c) because the model prevents other scientists from asking questions d) because the model requires the audience to pay full attention to it i don't know what to choose because between a and d a is much more likely than d because it only wants to get the attention of the audience. i'm confuse.

To find the inverse of a number a, one can use the equation f(c) = a-1/c=0 where c is the inverse of a use the secant method of finding roots of equations to find the inverse of a = 2.5 ,er = 0.001%