Hey, I am able to help you today :)
Step 1 - Simplify:
420x^2 - 18 = 2082
Step 2 - Add 18 to both sides:
420x^2 = 2082 + 18
Step 3 - Simplify 2082 + 18 to 2100:
420x^2 = 2100
Step 4 - Divide both sides by 420:
x^2 = 2100/420
Step 5 - Simplify 2100/420 to 5
x^2 = 5
Step 6 - Simplify:
x = 5
Step 7 - Check your answer:
10 x 42 x 5 - 18 =2082
Hope this helps you today :)