It looks like overkill to use the calculator to solve this first order linear equation but I will show you how to use the Solve function available on this calculator.
First solution: Pen and paper.
Use the properties of proportions:
Let a, b, c, and d numbers, with b, and d not equal to 0
if a/b=c/d then a*d=b*c
To apply it to your case, you set a=2.5, b=7, c=x, and d=10.
This gives 2.5*10=7*x
Dividing both members of the equation by 7 yields x=25/7.
Using the SOLVE program
- Calculator should be in computational mode: Press [MODE][1:COMP]
- Type in the equation in the way described below:
- You will need to use the key sequence [ALPHA][CALC] (=) to insert the = sign, the one at the top left, not the one at the bottom right.
- You will need to use the sequence [SHIFT][CALC] (SOLVE) to order the calculator to start solving your equation.
- You will need the key sequence [ALPHA] [)] to insert the X variable.
- Now that you have been alerted to the sequaences you will need, here is how to enter your equation.
- 2.5/7 [ALPHA][CALC] (=) [ALPHA] [ ) ] (X) /10
- While the above sequence is in the command line with the cursor still blinking to the right of the 0, press [SHIFT][CALC] to access the (SOLVE) command.
- The calculator displays in the top line of the dispaly "Solve for X". At the bottom there would be some old (irrelevant value).
- At this point you are expected to enter a value for your initial guess.
- You can for example enter 2 and press [=] at the bottom right. If you do not type a guess, the calculator uses the old (irrelevant) value as initial guess.
- So you enter initial guess 2 and press the [=/EXE] key at the bottom.
- After a while (could be short , if the initial guess is inspired) the calculator returns with the solution.
- The solution display screen recalls your equation on the top line,
- X=3.571428571 on the middle line, and
- L-R= 0 on the bottom line.
The L-R=0, tells you that the difference between the LEFT side and the RIGHT side of your equation is 0. That means the X given in the second line is the solution within the tolerance of the calculator.
If you are not happy with the solution (L-R different from 0), or the calculator failed to return a solution, you can press [SHIFT][CALC] (SOLVE) to restart with a better guess.