Answer:
the 8% loan has a principal of $37500
the 12% loan has a principal of $12500
Step-by-step explanation:
Let's start by writing the general equation for the interest hwre I is the interest, P is the principal (in our case would be loan amounts), "r" is the interest rate in decimal form (in our case one would be 0.12, and the other one 0.08), and t is the time in years (in our case 1 year).
![I=P*r*t](https://tex.z-dn.net/?f=I%3DP%2Ar%2At)
Then we write the interest equation coming from each loan at the end of this year (we call I1 the interest coming from the 12% loan and I2 the interest coming from the 8% one). Since we don't know the loan amounts (in fact those are what we need to find) we will name one "x" and the other "y":
![I=P*r*t\\I1=x * 0.12*1\\I2=y*0.08*1](https://tex.z-dn.net/?f=I%3DP%2Ar%2At%5C%5CI1%3Dx%20%2A%200.12%2A1%5C%5CI2%3Dy%2A0.08%2A1)
Next, we add these last two equations term by term, and replace the addition of both interests by $4500 as given in the information:
![I1=x * 0.12*1\\I2=y*0.08*1\\I1+I2 = 0.12x+0.08y\\4500=0.12x+0.08y](https://tex.z-dn.net/?f=I1%3Dx%20%2A%200.12%2A1%5C%5CI2%3Dy%2A0.08%2A1%5C%5CI1%2BI2%20%3D%200.12x%2B0.08y%5C%5C4500%3D0.12x%2B0.08y)
This is our first equation in the variables x and y which are our unknowns.
Now we generate the second equation on x and y by writing in agebraic terms the other piece of information we have: "the total of the two loans is $50000. That is the addition of the principals x and y should equal $50000:
![x+y=50000](https://tex.z-dn.net/?f=x%2By%3D50000)
We solve for y in this last equation and replace its form in terms of x in the equation of the interest, and solve for the unknown x:
![y=50000-x\\4500 = 0.12x +0.08 y\\4500=0.12x+0.08(50000-x)\\4500=0.12x+4000-0.08x\\4500=0.12x-0.08x+4000\\4500=0.04x+4000\\4500-4000=0.04x\\500=0.04x\\x=\frac{500}{0.04} =12500](https://tex.z-dn.net/?f=y%3D50000-x%5C%5C4500%20%3D%200.12x%20%2B0.08%20y%5C%5C4500%3D0.12x%2B0.08%2850000-x%29%5C%5C4500%3D0.12x%2B4000-0.08x%5C%5C4500%3D0.12x-0.08x%2B4000%5C%5C4500%3D0.04x%2B4000%5C%5C4500-4000%3D0.04x%5C%5C500%3D0.04x%5C%5Cx%3D%5Cfrac%7B500%7D%7B0.04%7D%20%3D12500)
Therefore the amount of the loan at 12% is $12500
Now to find the amount of the second loan "y" we use the equation for the totals of the loans:
![x+y=50000\\12500+y=50000\\y=50000-12500=37500](https://tex.z-dn.net/?f=x%2By%3D50000%5C%5C12500%2By%3D50000%5C%5Cy%3D50000-12500%3D37500)
Therefore, the loan at 8% is $37500