How does the northern European plain contribute to diversity agricultural production in Europe

there are 35 white marbles

step-by-step explanation:

y- yellow marbles

4y + 5 = 45

subtract 5 from both sides

4y = 40

divide for from both sides

y = 10

plug in 10 to get 40 yellow marbles then subtract by 5 to get 35 marbles

thus there are only 10 yellow marbles

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.