We have to write the system of equations.
The cost of 3 apples and 7 tangerines is $2.10.
If A is the price of the apples and T is the price of the tangerine, we can write:
[tex]3A+7T=2.10[/tex]We also know that 4 apples and 3 tangerines cost $1.85, so we can write:
[tex]4A+3T=1.85[/tex]The system of equations is then:
[tex]\begin{cases}3A+7T=2.10 \\ 4A+3T=1.85\end{cases}[/tex]Answer: The equations of the system are 3A + 7T = 2.10 and 4A + 3T = 1.85.