Es fa amb dos passos:  2x + 3 = 7

1. Sumar o restar el terme independent als dos membres: «math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mn mathvariant=¨bold¨ mathcolor=¨#00007F¨»2«/mn»«mi mathvariant=¨bold¨ mathcolor=¨#00007F¨»x«/mi»«mo mathvariant=¨bold¨ mathcolor=¨#00007F¨»§#160;«/mo»«mo mathvariant=¨bold¨ mathcolor=¨#00007F¨»+«/mo»«mo mathvariant=¨bold¨ mathcolor=¨#00007F¨»§#160;«/mo»«mn mathvariant=¨bold¨ mathcolor=¨#00007F¨»3«/mn»«mo mathvariant=¨bold¨ mathcolor=¨#00007F¨»§#160;«/mo»«mo mathvariant=¨bold¨ mathcolor=¨#FF0000¨»-«/mo»«mo mathvariant=¨bold¨ mathcolor=¨#FF0000¨»§#160;«/mo»«mn mathvariant=¨bold¨ mathcolor=¨#FF0000¨»3«/mn»«mo mathvariant=¨bold¨ mathcolor=¨#00007F¨»§#160;«/mo»«mo mathvariant=¨bold¨ mathcolor=¨#00007F¨»=«/mo»«mo mathvariant=¨bold¨ mathcolor=¨#00007F¨»§#160;«/mo»«mn mathvariant=¨bold¨ mathcolor=¨#00007F¨»7«/mn»«mo mathvariant=¨bold¨ mathcolor=¨#00007F¨»§#160;«/mo»«mo mathvariant=¨bold¨ mathcolor=¨#FF0000¨»-«/mo»«mo mathvariant=¨bold¨ mathcolor=¨#FF0000¨»§#160;«/mo»«mn mathvariant=¨bold¨ mathcolor=¨#FF0000¨»3«/mn»«mo mathvariant=¨bold¨ mathcolor=¨#00007F¨»§#8660;«/mo»«mn mathvariant=¨bold¨ mathcolor=¨#00007F¨»2«/mn»«mi mathvariant=¨bold¨ mathcolor=¨#00007F¨»x«/mi»«mo mathvariant=¨bold¨ mathcolor=¨#00007F¨»§#160;«/mo»«mo mathvariant=¨bold¨ mathcolor=¨#00007F¨»=«/mo»«mn mathvariant=¨bold¨ mathcolor=¨#00007F¨»4«/mn»«/mstyle»«/math»

2. Dividir els dos membres pel coeficient de la x:  «math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mfrac mathcolor=¨#00007F¨»«mrow»«mn mathvariant=¨bold¨»2«/mn»«mi mathvariant=¨bold¨»x«/mi»«/mrow»«mn mathcolor=¨#007F00¨ mathvariant=¨bold¨»2«/mn»«/mfrac»«mo mathcolor=¨#00007F¨ mathvariant=¨bold¨»=«/mo»«mfrac mathcolor=¨#00007F¨»«mn mathvariant=¨bold¨»4«/mn»«mn mathcolor=¨#007F00¨ mathvariant=¨bold¨»2«/mn»«/mfrac»«mo mathcolor=¨#00007F¨ mathvariant=¨bold¨»§#160;«/mo»«mo mathcolor=¨#00007F¨ mathvariant=¨bold¨»§#160;«/mo»«mo mathcolor=¨#00007F¨ mathvariant=¨bold¨»§#8660;«/mo»«mi mathcolor=¨#00007F¨ mathvariant=¨bold¨»x«/mi»«mo mathcolor=¨#00007F¨ mathvariant=¨bold¨»§#160;«/mo»«mo mathcolor=¨#00007F¨ mathvariant=¨bold¨»=«/mo»«mo mathcolor=¨#00007F¨ mathvariant=¨bold¨»§#160;«/mo»«mn mathcolor=¨#00007F¨ mathvariant=¨bold¨»2«/mn»«/mstyle»«/math»

Cal simplificar el resultat!