Răspuns :
7*x+7*(x+1)+7*(x+2)+7*(x+3)=154
7x+7x+7+7x+14+7x+21=154
28x+42=154
28x=154-42
28x=112
x=4
verificare: 7*4+7*5+7*6+7*7=28+35+42+49=154
7x+7x+7+7x+14+7x+21=154
28x+42=154
28x=154-42
28x=112
x=4
verificare: 7*4+7*5+7*6+7*7=28+35+42+49=154