问题 解答题 求未知数x x:12=15:8(4+15)x=3.5×1.2. 答案 (1)x:12=15:8, 8x=12×15, 8x÷8=110÷8, x=180;(2)(4+15)x=3.5×1.2, 4.2x=4.2, 4.2x÷4.2=4.2÷4.2, x=1.