Isaac and Paul shared some baseball cards in the ratio 2:5. If Paul gave 30 cards to Isaac, they would have the same number of cards. How many cards did Isaac have in
the beginning?

40% off the regular price is the correct answer.

step-by-step explanation:

, and

for

step-by-step explanation:

we can analyze the pattern at which the terms increase. let us denote , , , so that we can call

note the following:

the pattern: to get the next term value, we just add the next term number (e.g. 1st, 2nd, to the previous term value (term values are the given numbers in the question, 1, 3, 6, 10, 15,

from , to get to , we add

from , to get to , we add

etc.

we need to form a recursive formula, a formula that has the next term as a function of the previous term. so a possible recursive formula can be

, and for

a

step-by-step explanation:

b

step-by-step explanation: