Type each equation into Desmos and read the intersection. Those coordinates are the solution. You do not have to substitute by hand on the digital ACT. What the calculator can and cannot do is in Desmos on the ACT.
How to enter it
Put the first equation on line 1 and the second on line 2, in the form you were given. Click the point where the graphs cross. For y = 2x + 1 and y = −x + 7, the intersection is (2, 5), so x = 2 and y = 5. If a line is in standard form, type it that way. Desmos will graph Ax + By = C.
No intersection means no solution. The same line drawn twice means infinitely many. The algebra version of this topic is in systems of equations.
When this is the wrong tool
A quadratic you only need to factor is often faster by hand, and that graph is in quadratics in Desmos. One-step arithmetic still should not open the keypad. That cutoff is in when not to use Desmos.
The bottom line
Two equations, two lines, one click on the crossing. Read both coordinates before you pick the choice.
Start practicing
Start with a free diagnostic, then drill your weak spots with 15-question quizzes and track how you're doing across Reading, English, and Math. Compare plans whenever you're ready to go further.
This article offers general ACT prep guidance. The ACT can change from year to year, including its format, scoring, policies, test dates, and fees, so always confirm the latest details on the official ACT website at act.org before you make decisions. ACT® is a registered trademark of ACT, Inc. thirty-six is not affiliated with, endorsed by, or sponsored by ACT.