Ok, I checked my lessons. Here is how I did this:

Let's get the present value of everything at 30th birthday.

First, Take the present value of the first child's college expense annuity. A 4 year annuity with first payment of 10000 increasing by 1000 for a term of 4 years.

Arithmetic Annuity Immediate Present Value

Use the Present Value button. 13 for interest rate, 10000 for first payment, 4for number of periods, and 1000 for arithmetic payment. We get 33753.92 Present Value at age 40. Now, we need to discount that back to age 30. At 13% universal savings account rate that you give, we get 1/(1.13^10) = 0.294588348 Multiply this by our Present Value at age 40 and we get 9,943.51.

Now, our 2nd child's annuity is the same parameters as above, but 15000 is the first payment. Simply change your 10000 to 15000 and press Calculate. We get a Present Value at age 45 of 48626.27. Doing our discount factor 15 years back to age 30 gives us 1/(1.13^15) = 0.159890753. Multiply this by our Present Value at age 45 and we get 7774.89.

Now, our last Present Value to bring back to age 30 is our dad's retirement account. Go here:

Annuity Immediate Present Value

Calculate Present Value, 13 for interest rate, 50000 for payment, and 20 for n and press Calculate. Our Present Value is 351237.58 at age 60. We need to bring this back 30 years to our dad's 30th b-day. Discount factor is just like above, 1/(1.13^30) = 0.025565053. Multiply this by our Present Value of retirment payments at age 60, and we get 8979.41.

Now, we add up our 3 present value of payment streams at age 30 to get:

9,943.51 + 7774.89 + 8979.41 = 26697.81. Now we forward march and cross the finish line. Your problem asks what EQUAL annual amount does he need to invest to meet this obligation?

He's age 30 now, and the entire payout ends at age 80. That's a 50 year term.

Return to this lesson:

Annuity Immediate Present Value

This time, calculate payment. Present value is 26697.81, interest rate is 13, and our term is 30. Our term is 30, because your problem stated he wants this money ready at age 60 for his retirement. Press Calculate and our answer is 3561.77.

Therefore, he would need to deposit 3561.77 on every birthday starting 1 year from now to meet the 2 kids obligations and his retirement obligation.

Let me know if this doesn't match your answer key, or doesn't sound right.