How do you write sentences 10+k=4K

K added to 10 gives you 4 times the value of K.

If you wanted to solve the expression:

Subtract both sides of the expression, right hand side (10+k) and left hand side (4K), by - k as you want to get rid of the variable to get simply 10 on the LHS.

10+k - k = 4k - k

If we want to subtract k from k then we get 0, and if we want to subtract k from 4k we get 3k. For the sake of simplicity think of k as an object saying if I subtract object A from object A I get zero, and so forth.

We are left with the expression:

10 = 3k

We divide both sides by 3 as to get rid of it from the RHS.

We get a solution 10/3 = k